Problem: - Motorn B230F smårycker under varm tomgång / Irrugular idle (The engine B230F shakes) with engine warm. Småryckningarna började någon gång under hösten / lägre temperatur = är problemet temp-givare i LMM? Är platina-tråden ok pga renbränningen? - Motorn smårycker under varm tomgång ibland och motorn är "stabil" under varm tomgång ibland. - Felcode: 2-3-2 Adaptiv lambdareglering, mager- eller fetanslag på tomgång. Indikeringen check engine är en nolla. Additiv kompensation/ tomgångs-CO. Nollställning av adaption ger ca 0,1 volt från lambdasonden <30 sekunder = mager luft-bensinblandning. - Reset adaption, kall motor: 0,2 V <1 minut stabilt, 0,3 V <1 minut stabilt, 0,7 V efter några minuter stabilt/ej rycker, intervallet 0,65 - 0,7 V smårycker lite, intervallet 0,0 (0,1?) - 0,7 V rycker (skakar). Observera att mät- instrumentets inre resistans är endast 40 kilo-ohm per volt och strömmen är endast ca 4,7 microA från ECU till jord. Referens- spänningen är ca 0,6 volt mellan ECU och jord. - Kall motor = stabil tomgång = rik blandning luft/bensin <14,7? - Varm motor = ryckig tomgång = mager blandning luft/bensin >14,7? - Varm motor = ryckig tomgång = rik luft-bensinblandning och tändökning? - Gasspjället är maximalt stängd efter grundtomgångs- kalibreringen ca 540 - 560 = vacuumluftläckage? - Is the ignition timing varied when the engine is warm? EZ-116 F: "Vid temperaturer under 55 grader celcius ges en temperaturberoende tändsänkning." LH 2.4: "Chokefunktionen ger en uppfetning upp till en motortemperatur av ca 60 grader celcius." https://en.wikipedia.org/wiki/Ignition_timing: "Engine combustion efficiency and volumetric efficiency will change as ignition timing is varied, which means fuel quantity must also be changed as the ignition is varied. After each change in ignition timing, fuel is adjusted also to deliver peak torque." EZ-116 F: "Vid tomgång är tändläget endast beroende av varvtalet". - Lossa kontaktdonet för spridare nummer ett: almost stall. Lossa kontaktdonet för spridare nummer två: no change. Lossa kontaktdonet för spridare nummer tre: a slight change. Lossa kontaktdonet för spridare nummer fyra: almost stall. Lossa ICKE kontaktdonet för tändstift pga oförbränt bränsle når katalysator/lambdasond. Tändföljd: 1-3-4-2. Maybe this is the solution: - Att byta den smala slangen yd 9 mm to intake mainfold (to the orifice) på grund av att den inre diametern var endast 2-3 mm som låg an mot insugningsgrenröret. - Att byta tätningsringen 045.721 för oljelocket. - Att byta tändstiften efter ca 5200 mil (2016 - 2023) från Volvo 1367528 5N 8-13 kilo-ohm till NGK 7822 BPR6ES 5 kilo-ohm 6? Spanner size: 20,8 mm, thread size: M14x1,25, new plug: 1/2-2/3 turn (180 to 240 degrees), reused: 1/12 turn (30 degrees), 25 Nm ej anoljad. - Att justera grundtomgångsvarvtalet till 500 -+20 varv per minut (480 - 520). Jag kan inte minska grund- tomgångsvarvtalet till 520, endast ca 540 - 560 pga motor-stopp (CO-halten? Mager?). - Vacuumläckage cylinder 2 och 3. https://community.cartalk.com/ t/retorquing-bolts-after-gasket-replacement/193587/89 Intake mainfold, mutter, åtta stycken, åtdragningsvinkel ca 1/8 - 1/4 pga. sättning hos det klämnda materialet, dvs. en del av den elastiska deformationen blir permanent. De visko- elastiska materielen tätningar (packningar), målade ytor etc. ger elastisk deformation. - Spjällhuset, mutter, tre stycken, åtdragningsvinkel ca 1/32 - 1/16. - Att byta tändkablaget från Volvo Bougicord 403 class F 3 - 3,5 kilo-ohm 3 kilo-ohm för 59 cm till NGK 8840 RC-VL602 (8840 NGK RC-VL611 likströmsresistansen 1,3 - 1,6 kilo-ohm, 2 kilo-ohm för 63 cm). - Tändspolens primärlindning: 0,70 ohm, ok = 0,6-0,8, sekundärlinding: 7 kilo-ohm, ok = 6,9-8,5. - Rengöra LMM (luftmassameter) / MAF (mass air flow sensor). The platinum hot wire element was contaminated eller temperaturgivare. "CRC® mass air flow sensor cleaner" cleaned the contaminated platinum hot wire element och LMM´s temperaturgivare. - Is it too much oxygen/hydrogen in the petrol? Can the ECU compensate -+ 25% but after that then the code 2-3-2 is set? - Robert Bosch, workshop manual, Porsche, K-Jetronic, page nr 11, vacuum leaks: "... coat all air fittings (arrowed below) with soapy water. Bubbles indicate a leak." Efter concentrerad såpa och pluggat rör och kall motor: kontrollera avgassystemets tätningar, speciellt den mellan topplockets grenrör med fyra rör och den med två rör. - Byta packningen (tätningen) från 3531326, tjocklek: 1,6 mm, till flänspackning WAL-81041, tjocklek: 1,5 mm. - Kontrollera bränsle- och rest-tryck (läckage insprutnings- och/eller kallstart-ventil). Bränsletrycket ökar snabbt till ca 302 kPa (2010: ca 308 kPa) = filter ok. Rest-tryck ok = pump idrift: ca 302 kPa, pump icke idrift: ca 290 kPa, efter stilleståndstiden 20 minuter: ca 260 kPa. "Trycket får inte sjunka under 200 kPa på kortare tid än 20 minuter.". Pumpens backventil fungerar ibland, ibland inte. Om problemet fortsätter med pumpens backventil: slangen från bränsle- pumparna lossad och en slang med en luftnippel inkopplad, för att kunna pumpa upp trycket med en luftpump. - Mäta bränsletrycket under tomgång, i dellastområde och fullast: 235-(-60)≈ 295 kPa - 310-(-0)≈ 310 kPa. - Mäta temperaturgivarens resistans från kupén: LH 2.4: #13 och #5 (jord): ca 2,5 kiloohm, EZ-116 K: #2 och #20 (jord): ca 2,6 kiloohm, efter motorvärmare ca 3 timmar och ca -17 grader celsius. - Reinstall the temperature sensor, installation torque: 25 Nm, because of "Electrolytic series: During contact of different metals, galvanic action, assisted by humidity, develops. ..." - Kontroll av stompunkter/stomanslutningar. B 230 F LH-Jetronic 2.4: Stomanslutning nr 1 på insugningsgrenröret: signaljord: styrenhet ansl 5, styrenhet ansl 19 (bygel), styrenhet ansl 29 (bygel), styrenhet EZ-116 K ansl 20, luftmassameter, diagnosuttag. Stomanslutning nr 2 på insugningsgrenröret: effektjord (slutstegsjord): styrenhet ansl 17, tomgångs- och fullastbrytare, lambdasond uppvärmning, styrenhet EZ-116 K ansl 14, slutsteg EZ-116 K. - Kompression, varm motor, utan luftfilter, öppet gasspjäll: 2024-01-19: 1: 14,1 2: 14,7 3: 14,6 4: 14,5 bar. 2010-04-28: 15 bar alla cylindrar. Optilux compression tester 8PD 004 838-001. - Unequal fuel delivery between cylinders (see comparative test). Injected fuel quantities unequal: check for equal fuel quantities. Insprutningsventil nr 1: 97,5 ml/32,7 sek -> 178,9 ml/min vatten. Nr 2: 96 ml/32,5 sek -> 177,2 ml/min vatten. Nr 3: 97 ml/32,7 sek -> 178 ml/min vatten. Nr 4: 97 ml/33,2 sek -> 175,3 ml/min vatten. Efter ultraljudsrengöring men icke backspolning: Insprutningsventil nr 1: 97,5 ml/33,5 sek -> 174,6 ml/min vatten. Nr 2: 98,5 ml/33,2 sek -> 178,0 ml/min vatten. Nr 3: 98 ml/33,4 sek -> 176,0 ml/min vatten. Nr 4: 97 ml/33,0 sek -> 176,4 ml/min vatten. Spridarens ström är ca 0,6 A vid spänningen ca 12 VDC. Insprutningsvolym "214 cm3/min vid systemtryck 300 kPa (losstagen ventil får endast provas med speciell utrustning)." - Lambda control system not functioning correctly: check lambda control system. Varm motor, dellast under ca en minut för uppvärmning av O2-givare, reset adaption, tomgång, lambdasondspänningen icke över 0,1 V men ibland transienter över 0,1 V, efter ca x minuter sätts 1-1-3 och indikeringen check engine ettställs. LH 2.4: felkod 1-1-3 lambdareglering för mager eller fet eller lambdasondsignal konstant låg eller hög. Mätbox, signalbeskrivning: "Styrenheten kan inte kompensera insprutnings- tiden och motorn går antingen för fett eller för magert." Volvo system tester, running test, felmeddelande, LH #24, lambdasondsignal felaktig: "Felmeddelandet lagras om spänningsskillnaden mellan hög och låg signal har varit mindre än 0,3 V..." Felkod 1-1-3 återkommer inte pga lambdasondens spänning är ok och pendlar eller "... to generate a high-low switching voltage." eller "... a binary ‘high’ or ‘low’." Förvärmningsspänning ok. Tomgång och/eller dellast: förvärmnings- strömmen ca 1,3 A. Reset adaption, förvärmning urkopplad, endast 0,6 V, efter några minuter 2-1-2/check engine, reset 2-1-2, dellast några minuter, ej 0,1-0,9V endast 0,6V utan förvärmning, tändning från/stopp, tändning till/start ger 2-1-2 och check engine. Med förvärmning: 2-3-2, 0,11-0,86V. Lambdasond svart/sot. 2010: förvärmningsstartströmmen 3,6 A. Lambdasond, Volvonummer: 3501732-2 / 3501753, Boschnummer: 0 258 003 034. "Resistans i förvärmningsmotståndet: kall sond (+20°C): 3 ohm, varm sond (över 350°C): 13 ohm. Åtdragningsmoment: 55 Nm. Bultförbandspasta, Volvo- nummer 1161035-9, ska strykas på sondens hela gängade del."CRCkopparpasta - Ny lambdasond men en pirat från Skruvat.se men från 2010, art.nr.: 11470, 390 SEK, förvärmningsström ca 0,8 A och spänning ca 0,11-0,89V. Än så länge saknas felkoden 2-3-2 och motorn smårycker mycket mindre nu under tomgång men ryckningarna finns där fortfarande men i perioder, som om lambdasonden är trög, inte en tillräcklig snabb spänning till ECU eller är "problemet" den så kallade "Oxygen sensor feeback 'closed loop' ('action circle') system". Jag köpte en annan piratdel år 2010 också men en LMM från Skruvat.se, produktid: 10948, 1490 SEK, men den hade en urusel funktion under tomgång och en växel ilagd och en varm sommardag. Motorn ökade vridmomentet snabbt för att sedan snabbt minska. Motorn började oscillera så mycket att jag höll fast mig i ratten... Aldrig mera piratdelar!!! Felkoden 2-3-2 återkommer och motorn smårycker under varm tomgång. Har lambdasond-pirat-Skruvat.se-!"#¤%&/() inte uppnått driftstemperatur under varm tomgång???!!! Motorn smårycker mycket mindre under varm tomgång efter landsvägskörning/dellast. Volvo, 3501753, resistans i PTC, +21°C: 2,2 ohm. Skruvat.se, 11470, www.proparts.se, 25003000, EAN 7340024602488, resistans i PTC, +21°C: 4,5 ohm. Bosch universal oxygen (O2) sensor 0 258 986 504 (?15737?), resistansen 2,15 ohm i PTC vid +21,5°C, förvärmningsströmmen 1,36 A under varm tomgång, spänningen 0,07 - 0,83 V vid varm tomgång. Än så länge saknas felkoden 2-3-2 och motorn smårycker mycket mindre nu under varm tomgång. Felkoden 2-3-2 återkommer och motorn smårycker ibland och ibland icke under varm tomgång: !"#¤%&/(). CO tomgång: ?, CO 2500: ?, HC: ?, lambda: ? - Vacuumläckage cylinder nr 1 mellan insugningsgrenrör (intake mainfold/ inlet manifold) och cylinderhuvud (topplock/cylinder head). "An air leak in the intake manifold gasket.""Do not replace the upper intake manifold gaskets with the original orange gasket material..." because of E85. - Att justera/kalibrera GRUND-tomgångsvarvtalet till 500 -+20 varv per minut (480 - 520). - Ok? Har jag förstått följande sekvens rätt?: 1. Startmotor. 2. LMM mäter gasspjällets och vevhusventilationens luftmassa. 3. Bensin. 4. Gnista. 5. Tomgångsventilens referensvärde är spjällets + ventilationens luftmassa. 6. Tomgångsventilen reglerar från referensvärdet (motorn nästan stannar om tomgångsventilens slang stryps) till tomgångsvarvtalet 775 -+ 50 varv per minut, varm motor, ej justerbart. Källa/Source: - Volvo servicehandbok, avd 2 (23), bränslesystem LH-Jetronic 2.4, motor B230F, 240 1989-19.. - Volvo servicehandbok, avd 2 (23, 28), bränslesystem LH 2.4/LH 3.1, tändsystem EZ 116 K, 240 1989- - Volvo servicehandbok, avd. 3 (39), kopplingsschema, 240 1990, augusti 1989. - Haynes service and repair manual. Volvo 240 series 1974 to 1993 (up to K registration) petrol. - Robert Bosch, trouble-shootning chart, K-Jetronic, Porsche. - Robert Bosch, workshop manual, Porsche, K-Jetronic. - Mager blandning kräver bättre gnista. R&T 1976/12 och Radio & Television 1979 bygg själv nr 5, s 65. - Bulten katalog 89, teknisk information, förspänning och åtdragningsmoment. - https://www.youtube.com/watch?v=o90KcZRz95U - https://en.wikipedia.org/wiki/Mass_flow_sensor - https://extension.psu.edu/fuel-ethanol-hero-or-villain#:~:text= Ethanol%20molecules%20include%20oxygen%20atoms%2C%20whereas%20gasoline%20molecules,is%20more%20oxygen%20available%20in%20the%20fuel-air%20mixture. - ENERGILÄRA, Grundläggande termodynamik för högskolestudier, Olof Beckman, Bengt Kjöllerström, Tage Sundström, Almqvist och Wiksell, AB Grafisk Press, Stockholm 1984, ISBN 91-20-06171-4: 12.4.1 Ottocykeln: "Den kallas ibland konstant volym cykeln, eftersom förbränningen approximativt sker vid konstant volym.". 12.4.2 Dieselcykeln: "I dieselmotorn sker förbränningen teoretiskt vid konstant tryck.". Förord: "I nyfikenhetens laboratorier försvinner den meningslösa uppdelningen mellan teori och praktik, för bägge är lika spännande och ingendera är förlamande självklar." Krister Stendahl. - Table 19: Electrolytic series. Sauer, Hans: Modern relay technology / Hans Sauer. [Transl. from the original German "Relais-Lexikon" by J. G. Naples]. - 2. ed. - Heidelberg: Huethig, 1986. Einheitssacht.: Relais-Lexikon (engl.) ISBN 3-7785-1251-X. Published by © 1986 Dr. Alfred Huethig Verlag GmbH, Heidelberg. Printed in Germany. CIP-Short title adaption of West German library. Translated from the original German "Relais-Lexikon" by Mr. J. G. Naples, SDS-Relais Ltd., Milton Keynes, England. https://bkg405h.nfshost.com/Electrolytic_series_Hans_Sauer.tif - https://en.wikipedia.org/wiki/Ignition_timing https://en.wikipedia.org/wiki/Ignition_timing#/media/File:Pressure_patern_in_dependence_on_ignition_timing.svg https://en.wikipedia.org/wiki/File:Pressure_patern_in_dependence_on_ignition_timing.svg - Niterra India PUT. LTD. https://www.ngkntk.in/installation-instructions/ - https://www.denso-am.eu/products/engine-management-systems/lambda-sensors#:~:text=Lambda%20sensors%20work%20constantly%20to%20keep%20the%20air-fuel,function%20optimally%20and%20keep%20emissions%20to%20a%20minimum. - 2008?: http://www.bilhobby.se/forum/viewtopic.php?f=13&t=1220 Hejsan, jag vill beskriva hur viktigt det är med ett rent spjällhus och vevhusventilation på Volvo 740 och 940 som i grunden är oljans fel! Samma problem finns på dagens bilar, men nu har man uppmärksammat hur viktigt det är med rätt olja... Vanlig kundanmärkning vid kallt väder på vintern är att bilen startar till men dör direkt, startar sen inte mer, stiften blir sura Är dom uppe i fjällen och åker skidor så verkar det vara regel inte undantag, bogsering till verkstad, in i värmen, byte av tändstift ( även nya och rätt tändstift byts, gamla ska bytas) bilen startar.. allt är bra. Det säljs mycket tändstift i onödan. Vad händer? Jo, motorn får bensin men ingen luft...Det som ger luft är en liten glipa i spjällhuset tillsammans med vevhusventilationen ger en grundmängd med luft vid start, efter grundmängden luft kopplas tomgångsmotorn in som har grundmängden som referens, alltså grundmängden + tomgångsmotorn ger tillsammans rätt mängd luft, tomgångsmotorn måste ha grundvärdet som referens...Skulle man tillföra lite mer luft genom att röra gaspedalen, så kopplas kallstartsfunktionen ur helt genom att spjällkontakten påverkas Alltså gör rent spjällhuset och vevhusventilationen ordentligt från koksavlagringar och skit från DÅLIG olja. Riktig olja ger inga koksavlagringar.... Vid kontroll om grundvärdet (referensluften) är rätt. Förutsatt att motorn är övrigt OK... Varmkör motorn, nyp ihop slangen absolut HELT som går till tomgångsmotorn. Motorn ska då knapt gå på tomgång utan att stanna, då är det bra, men stannar motorn direkt så är det fel värde. Man ska nypa ihop slangen sakta så motorn hinner med att ställa om, man skall oxå ta ur och i säkring ett för att nollställa motorn före och efter testet. Räcker inte rengöring så får man grundinställa spjällhuset, men det rekommenderar jag inte att man gör utan noga förberedelser... - https://forum.mustangclubsweden.org/topic/16047-grundt%C3%A4nk-f%C3%B6r-t%C3%A4ndning/ Grundtänk för tändning. --- Till att börja med: En magrare bränsleblandning antänds långsammare, en fetare snabbare. Mycket viktigt att komma ihåg. --- JanneJ JanneJEnthusiast - https://forum.savarturbo.se/viewtopic.php?t=57713&sid=f8af1a3364d405c67b848b366e9cef63 Re: B230 små misständningar .mm Post by Pacman » Mon Aug 22, 2011 8:31 pm --- Låter som att motorn nyser och allt stannar upp en förbränningstakt. Isf går den för magert. Småryckningar brukar tyda på att den går fett.--- //Pacman (Patrik Ståhl) - https://forum.savarturbo.se/viewtopic.php?p=554314&hilit=sm%C3%A5rycker#p554314 De flesta motorer går ryckigt och konstigt med för lite tändning på extra låga laster, det brinner väldigt långsamt när det inte är så mycket luft i cylindrarna så man ska tända på tidigt. Mattias Säfsten (fd Sandgren) --- - https://club.autodoc.se/magazin/sa-kontrollerar-du-tandsystemet --- 4. Ett poppande ljud hörs från insugningsgrenröret eller ljuddämparen. Detta inträffar på grund av felaktigt justerad tändning efter dåligt reparationsarbete. Att använda tändstift med felaktig värmeklassning kan också orsaka främmande ljud. --- - https://www.sunautoservice.com/about-us/shop-talk/why-your-engine-is-running-lean-how-to-fix-it/ ... manifold air pressure sensor (MAP), and the EGR (exhaust gas recirculation) sensor. Mass Airflow Sensor (MAF) - https://kdxrider.net/forums/viewtopic.php?t=14222 What do rich and lean sound like? Rich = sputtering/popping/crackling Lean = bog/lug/booooooha - https://www.quora.com/How-does-a-car-run-if-it-has-too-much-ignition-timing#:~:text=Clues%20that%20the%20timing%20is,sign%20of%20too%20much%20advance. How does a car run if it has too much ignition timing? Bob Faestel Lives in Theresa, WI (2004–present) I'm not quite sure what you are asking whether you me as n what are the symptoms or how is it possible. It's possible because maybe the timing is only advanced a couple degrees which really wouldnt even be noticable. Generally you have a relatively large window of ignition timing where the engine will still run. Clues that the timing is too advanced would be hard cranking, the engine tries to kick back when cranking, rough idle can be caused by too much advance, and detonation is another sign of too much advance. - https://upload.wikimedia.org/wikipedia/commons/1/12/ Pressure_patern_in_dependence_on_ignition_timing.svg https://en.wikipedia.org/wiki/Ignition_timing --- There are many factors that influence proper ignition timing for a given engine. --- ... and engine temperature... --- The ignition timing is also dependent on the load of the engine with more load (larger throttle opening and therefore air:fuel ratio) requiring less advance (the mixture burns faster). Also it is dependent on the temperature of the engine with lower temperature allowing for more advance. --- - https://www.quora.com/How-does-engine-coolant-temperature-affect-ignition-timing-on-a-gasoline-engine How does engine coolant temperature affect ignition timing on a gasoline engine? James Kulik --- Rates of reaction, like the speed fuel burns are directly related to temperature. Thus a increasing the temperature will speed up the rate. The timing would need to retarded to stop detonation should the combustion temperature increase. --- - https://www.hpacademy.com/courses/practical-standalone-tuning/step-6-idle-tuning-idle-ignition-timing Idle Ignition Timing --- 01:50  If you have an engine that is heavily modified, and particularly one with a large cam that provides a lot of overlap, you'll usually see more stable idle speed control with a slightly more retarded ignition timing. --- - https://www.physicsforums.com/threads/ignition-timing-vs-heat-distribution-in-the-engine.701885/ Jul 21, 2013 #5 thender Follow-up --- I keep studying this topic because it's very important to understanding modern engine controls, for example it seems that the timing is often retarded at startup to help achieve a rapid catalyst warmup. During idle conditions the timing may be controlled in order to vary the torque output to maintain a given speed. Which I think has to do with the relationship of the Location of Peak Pressure and the crank angle for maximum mechanical advantage, which seems to be dependent on the ignition timing and engine speed. Ignition timing is also used in traction control systems I believe to modulate engine torque. Thanks for help with this topic and I appreciate any further insights, -Andrew Jul 23, 2013 #6 Damo ET You seem to have a good handle on what to expect and why. I would reccomend googling 'mass fraction burned' to give more insight into combustion behavior. It becomes very clear that unburned charge can make its way out of the chaimber with too little ignition timing. The time for complete charge burning varies with mixture strength, cylinder pressure and temp, and the octane of the fuel. To get the whole shooting match just right is a delicate balance. It is easy to see with a wideband lamda sensor and display, while tweaking ignition timing realtime. Idle mixtures can change from 13:1 with 12deg timing to >18:1 by adding 10-15deg of timing(that is without touching fueling!). Also, one of the reasons that retarded ignition timing is used at idle is to ensure a steady solid idle. The engine will pick up quite a bit of torque and rpm if the idle timing is advanced from 5-10 degrees, bit this comes at a cost of instability as engine temps change and altenator loads fluctuate. So a trade-off is struck with less efficient and ecconomical timing, for the benefit of a rock solid idle. - https://www.autospeed.com/cms/a_2717/article --- Another reason that detonation might be a danger is if you’re running a load interceptor to adjust mixtures. Lean out the top end and the ignition timing will also advance – another potential cause of detonation. --- - https://en.wikipedia.org/wiki/Oxygen_sensor --- Sensor failures --- For heated sensors, normal deposits are burned off during operation, and failure occurs due to catalyst depletion. The probe then tends to report lean mixture, the ECU enriches the mixture, the exhaust gets rich with carbon monoxide and hydrocarbons, and the fuel economy worsens. - https://www.hella.com/techworld/uk/Technical/Sensors-and-actuators/Test-lambda-sensor-4379/# The lambda sensor principle is based on an oxygen comparison measurement. This means that the remaining oxygen content of the exhaust emission (approx. 0.3 – 3 %) is compared with the oxygen content of the ambient air (approx. 20.8 %). If the remaining oxygen content of the exhaust emission is 3 % (lean mixture), there is a voltage of 0.1 V due to the difference compared with the oxygen content of the ambient air. If the remaining oxygen content is less than 3 % (rich mixture), the sensor voltage rises to 0.9 V in proportion to the increased difference. The remaining oxygen content is measured using various lambda sensors. The function of the lambda sensor is usually checked during the routine exhaust emissions test. However, since it is subject to a certain amount of wear, it should be checked at regular intervals to ensure that it is working properly (approx. every 30,000 km) – e.g. as part of the inspections. The tightening of laws to reduce vehicle exhaust emissions has been followed by an improvement in the technology for exhaust aftertreatment. Voltage jump probe This probe consists of a finger-shaped, hollow zirconium dioxide ceramic element. The characteristic feature of this solid electrolyte is that it is penetrable for oxygen ions at a temperature higher than approx. 300 °C. Both sides of the ceramic are coated with a thin, porous layer of platinum which works as an electrode. The exhaust emissions flow past the exterior of the ceramic element, while the interior is filled with reference air. The properties of the ceramic element mean that the differing oxygen concentration on both sides causes a migration of oxygen ions, which in turn generates a voltage. This voltage is used as a signal for the control unit, which changes the air-fuel ratio depending on the residual oxygen content of the exhaust emissions. This process of measuring the remaining oxygen content and making the mixture richer or leaner is repeated several times per second, generating a demand-based mixture ( λ = 1). - https://www.bosch-mobility.com/en/solutions/sensors/switching-type-lambda-sensor/ --- The switching-type lambda sensor identifies this stoichiometric point and generates an immediate output signal jump during the transition from lean to rich operation. --- - https://www.boschautoparts.com/p/rich-burn-oxygen-sensor Rich Burn Oxygen Sensor Standard narrow band type Oxygen Sensors operate between 0 and 1 volts, and are only capable of accurately measuring a stoichiometric air/fuel ratio (e.g. 14.7:1). A richer or leaner condition results in an abrupt voltage change and is only useful for qualitative determination. Frequently Asked Questions What is the difference between rich burn and lean burn sensors? The Rich Burn is a standard narrow band type oxygen sensor and is only capable of accurately measuring a stoichiometric air/fuel ratio (e.g. 14.7:1). The Lean Burn is a planar ZrO₂ two-cell limit current sensor with an integral heater suitable for measuring the oxygen content and the λ value of exhaust gases in vehicle engines. - Installation: Bosch O2 Sensor with SmartLink™ https://youtu.be/ex1Hki6-NHw https://www.mekonomen.se/lambdasond-universal-bosch-13969082 - https://www.boschautoparts.ca/p/premium-oxygen-o2-sensors-0258986001- --- Support Catalog Oxygen Sensors One-wire and two-wire “unheated” type oxygen sensors should be checked or replaced every 30,000-50,000 miles. These sensors rely solely on hot exhaust gas to heat up to operating temperature, and therefore are designed to allow a large volume of exhaust gas to make contact with the active ceramic element. Therefore, these sensors are exposed to contamination, especially the “wide-slot” varieties found on Chrysler, Ford, and General Motors vehicles. “Heated” type oxygen sensors have a built-in heater which heats the sensors up to operating temperature. Therefore, much less exhaust gas needs to contact the ceramic element, making these sensors less pron to contamination. “Heated” type sensors can also be located further downstream (closer to the catalytic converter), which increases their life expectancy by reducing thermal shock. In addition, the latest versions feature improved ceramic elements which are more resistant to silicone, oil, and lead contamination. “Heated” type oxygens sensors should be checked or replaced every 60,000-100,000 miles. - https://www.garaget.org/forum/viewtopic.php?id=329674 Xebers76 9 juli 2019 Bara så alla har koll här nu: minus är efter TDC och inget minus är före TDC Vid tomgång så är ca 20 grader ganska normalt för dem flesta motorer. Grader på minussidan används när man ska få så kallat "pops n bangs" Har du kollat så markeringen stämmer med veven än? Senast redigerat av Xebers76 (9 juli 2019) - https://forum.savarturbo.se/viewtopic.php?f=16&t=76495 Re: Dålig signal vevaxelgivare Nira i7 Inlägg av Pacman » sön jun 23, 2013 11:36 am Kan bekräfta detta nu efter två hela dagars felsökande och brottande med en T5 och Nira i7x. För att göra allting enkelt: I nuläget klarar Nira i7x inte av att läsa den smala plastgivaren som sitter på 850 m.fl vitmotorer. Nira kämpar för fullt med att försöka lösa problemet. Snabbaste lösningen är att plocka en givare med hållare ifrån en nyare vitmotor. De är lite grövre, därav att man får byta hållaren med, men största skillnaden är magnetismen. Plastgivaren är knappt magnetisk alls. Metallgivarna i B230 och nyare vitmotorer är mkt mer magnetiska. //Pacman (Patrik Ståhl) - https://www.fixya.com/cars/t2289255-rough_idle_after_warm_up Rough Idle only when engine is warm Posted on May 28, 2009 Answered by a Fixya Expert Rough idle after warm up My 1991 cadillac devile(4.9) runs great when cold,but after it warms up it starts to run rough. No engine lights come on dash indicating a problem. I have also changed the air and fuel filter. the car has 102k. miles. Anonymous Cadillac Master Answers Posted on May 28, 2009 I'd take a look at the temp sender...the engines computer may be "thinking" the engine is still cold when it's not. That would cause it run rich (and rough) after it's warmed up. ... --- - https://en.wikipedia.org/wiki/Idle_air_control_actuator An idle air control actuator or idle air control valve (IAC actuator/valve) is a device commonly used in fuel-injected vehicles to control the engine's idling rotational speed (RPM). --- Problems with IAC Although the IAC is supposed to last the vehicle's lifetime, various reasons may cause it to fail/malfunction prematurely. The most common failure mode is partial/complete jamming of the actuator (due to dirt/dust or even oil) where it cannot be smoothly controlled. The result is an engine that fails to maintain idle RPM and frequently stalls. A jammed actuator may be freed simply by cleaning it. However an actuator that has stopped working due to a fault in its servomotor will need replacement. Air leaks in either the stepper housing or pipes will cause elevated idle RPM. - https://community.cartalk.com/t/can-anyone-help-me-interpret-scan-tool-data-for-rough-idle/150478/9 Can anyone help me interpret scan tool data for rough idle? Mustangman Oct 2019 Long term fuel trim seems to tell me you have a leaking injector. Too much fuel is getting in and the computer is trying to rectify it. The hard start sure sounds like a leaking injector bleeding off pressure. Doesn’t explain why iit doesn’t happen later. Maybe heat is binding up an injector internally only when hot. circuitsmith Oct 2019 Here’s another vote for a leaky injector(s). The symptoms fit. The IAC won’t throw off fuel trims or cause rough idle at 800-950 rpm. Hook up a fuel pressure gauge and watch the pressure when the engine is turned off. It should fall very slowly or not at all. tcmichnorth Oct 2019 I agree with @Mustangman and @circuitsmith. Long term is off. Checking how fast fuel pressure drops is key. Scrapyard-John Honda-Blackbird Oct 2019 --- I doubt the iac valve will fix it. But bad idle, it has an idle air control valve, I’d try it considering the effort is so minimal. Honda-Blackbird Oct 2019 If an injector leaked down… it would be cylinder specific and we would see hard misfires on that cyl. It should stick out like a sore thumb in this scenario. No? If this vehicle is known for cam sensor issues… then start there, test it, replace it… Because if the cam pulses are incorrectly correlated to the ecu so are the injector pulses… most likely early (possibly during exhaust event) which would produce a rich exhaust… which would then try to be leaned out… Or something along this line of thought. Or is it just late and I’m completely exhausted again? tcmichnorth Oct 2019 Honda-Blackbird: If an injector leaked down… it would be cylinder specific Good point. One other thing is that this car is difficult to start if it has sat for more than an hour. Delayed starting could come from a failed cam sensor also because the ECU had to guess compression tdc. Other thoughts: Another reason for delayed starting might be fuel pump check valve. A slightly leaking fuel pressure regulator can cause richness. Could be multiple problems? Rod-Knox Oct 2019 Without the Daewoo scan tool I would guess that an oscilloscope would be the best method to determine the operation of individual injectors. A digital scope would give a great deal of insight into the problem by viewing all the inputs and outputs involved with engine management. And a digital scope is useful for all makes and models. keith Oct 2019 Do you have a tach in your dashboard? If so, what is the idle speed? It should be around 750 rpm. If it is idling much below 700, then the rough idle could be due to the throttle position sensor (TPS). The TPS should have three pins on the connector and is easy to check with an ohm meter or VOM meter. Everyone should have one of these if you pan on repairing your own vehicles. --- Do also fix the P0442 issue because that could be allowing unmetered air into the intake manifold. George_San_Jose1 Oct 2019 If you solve the -10% and worse long term fuel trim problem you’ll likely also solve the poor engine performance. Too much gas getting into the engine: faulty injector, too high of fuel pressure, incontinent fuel pressure regulator diaphragm, faulty purge function in the evap system Inaccurate metering: faulty O2 sensor, faulty MAF or MAP sensor, faulty coolant temp sensor My guess is either a faulty purge function or MAF sensor. The engine is running at the correct “warm” temperature right? keith Oct 2019 --- If they don’t fix the problem you are not out that much. However, I’d still fix any air leaks that might allow unmetered air into the manifold first. - https://community.cartalk.com/t/mercedes-300ce-rough-idle/84937/4 Mercedes 300CE rough idle ok4450 May 2014 I’ve worked with CIS a lot and agree with db4690 completely. Air leaks and lousy injector spray patterns are a curse. While I don’t know if this is common with Benzes, I’ve seen older CIS SAABs have a slightly rough idle simply because whoever checked the engine oil level did not fully seat the oil dipstick in the tube. Not saying this is the cause here; only that CIS can be that finicky. H.D May 2014 --- @db4690: “…Have you used a smoke machine to rule out the false air? …” --- “Coil … tend to fail when hot”. --- H.D May 2014 --- Today I renewed both engine mounts and the transmission mount. --- The old transmission mount was about one third of an inch lower than the new one. --- With the new mounts the engine started almost without any shaking! Then I went on a test drive with a cold engine. With a cold engine idle was also okay with the old mounts. The result at 185°F: 80% of the rough / shaky / vibrating idle is absorbed by the new mounts! But obviously the old mounts were not the source of the vibrations, they just couldn’t absorb them anymore (or only very poorly). A little shaking is still detectable. You can feel “tiny kicks” every 2 or 3 seconds (only with the warm engine at idle in “D”). Above idle and moving the car really feels like new. So, I guess I’m not done yet! ok4450 May 2014 --- There’s always that nagging issue of an intake air leak. --- H.D May 2014 @ok4450 --- “…There’s always that nagging issue of an intake air leak. …” To be honest – that nags me too! That’s why I aditionally put a clamp on the hoses of the idle air control valve, when I reinstalled the valve after checking it yesterday. Originally they are just slipped over the connection nozzles of the valve and over the fitting on the air flow sensor housing. Since the hoses felt quite loose I thought it wouldn’t hurt to do that, although another brake fluid spray test at idle didn’t show any leak on them before I clamped them. But the clamps didn’t change anyway regarding those “tiny kicks” at idle. Btw: When I sit in the car with the hood completely opened, I can look at the top of the engine underneath the back edge of the hood. And every time when I feel a tiny kick through the seat and the steering wheel, I can see the engine shake a wee bit. “… the gauge needle should be rock steady. …” But only if idle is steady as a rock! – which it is not. And - even if it were – with an untouched false air leak, the manifold vacuum would also be constant, wouldn’t it!? ok4450 May 2014 At the risk of sounding like a stuck vinyl record, verifying beyond all doubt whether there are any vacuum leaks at all would still be a first step in my opinion. Overanalyzing things can be an easy trap to fall into. H.D May 2014 @db4690: --- @ok4450: I’m quite sure that there are no vacuum leaks anymore. There was one when I tested the whole intake system last fall, it was the injector seal of cylinder No. 5. However after renewing all 6 injector guide- and seal-sleeves when I tested the old injectors, there was no noticable improvement to the idle quality. But - since you suspect false air so emphatically, and since I don’t have a smoke machine, which db4690 suggested, I’m considering to buy a package of cigarettes. As a nonsmoker I just hope I’ll not become sick! db4690 May 2014 This is in regards to vacuum leaks and idle quality I have worked on numerous cars that had vacuum leaks, yet had an excellent idle After fixing the vacuum leaks . . . to correct maxed out positive fuel trim . . . the idle was the same ok4450 May 2014 I’ve also worked on cars with vacuum leaks that had an excellent idle and also ones with leaks and bad idles. My CIS experience has been mostly with VW along with a few Volvos and BMWs; not Benzes. A leak on a VW would mean a rough idle to some degree. The usual suspect was injector seals. I’m not saying that the OP should spend big bucks on a smoke machine that will be seldom used. A vacuum gauge is dirt cheap, easy to use, and may reveal any one of a number of faults that could cause a rough idle. I’ve seen a few rough idles caused by one weak cylinder head valve spring although I would tend to think that is not the case here. A gauge would show it though. H.D May 2014 @db4690 --- @ok4450 I agree with you, if you would use a vacuum gauge to check whether there is a leak somewhere. But then you would still have to locate it, for which smoke would certainly be helpful. Before I would test the intake system with a vacuum gauge, I better wait until after I renewed my o2-sensor first, because with the slow reaction of the current sensor at idle there’s to much flactuation in the idle speed in “P” or “N” now (625 - 725 rpm), causing a flactuation of the vacuum level too. Unless I use the parking brake and put the transmission in “D”, in which idle is very stable at around 540 rpm. Of course the vacuum level would be lower than too. I never used a vacuum gauge before. Where do you usually connect it? ok4450 May 2014 A vacuum gauge can be connected to any vacuum source from the intake manifold as long as it’s below the throttle plate; meaning between the throttle plate and the cylinder head. If a leak is suspected based on the gauge reading then one can start gently pinching off vacuum hoses with a pair of needle-nose pliers. That will at least steer you in the direction of the leak; assuming it’s not related to injector seals, intake gasket, etc. Fender1325 May 2014 In a complete bout of laziness, Im throwing something out there without reading all the responses so this may be a repeat BUT, A friend recently inherited a 190e and had rough running problems. After throwing parts at it, it turned out to be from a “sock” like filter inside the gas tank that was plugged up and closing from suction from the fuel pumps. Removal of that and washing out the gas tank cured it all. Apologies if this has already been suggested. H.D May 2014 @Fender1325 The 300CE gas tank is also equipped with that filter. The fuel pressure measurements were all in order and the car doesn’t show any problem or lack of power at full acceleration up to higher revs. So there doesn’t seem to be any filter problem neither with that filter nor with the one on the pressure side of the fuel pump and also not with the tiny filter at the entrance to the fuel distributor. Thank you for mentioning that! … And don’t hesitate to throw in suggestions! … Maybe you saw what I experienced with the engine oil level and the not sealing O-ring of the dipstick. Who knows if I would ever have found out about that, if ok4450 wouldn’t have talked about his experience with oil dipsticks and false air on CIS cars. Fender1325 Jun 2014 It sounds like you’ve gone through the whole fuel system and ensured thats all happy, and the ignition is all good as well, how about the cooling system? Are the fans coming on, new coolant, new radiator hoses? Sounds like heat is making the problem worse (sluggishness or rough idle). Outside of that then Id guess sensors of some sort. If you can go to a junkyard and grab some spare sensors or relays to try. Its beyond me really but if you’ve ruled out all the major components of the mechanical systems then it seems to be some computer issue. I have read on here the crank position sensor or cam sensor to be faulty when hot and cause rough running or hard starts and then when its cool the car magically starts no problem. H.D Jun 2014 @Fender1325 Everything you mention, I have tested – including the crank position sensor, which – as you say - can cause problems with rising temperatures. Especially the – luckily very rare - stalling at idle and hard restarting when the engine was hot could also be caused by the crank position sensor. As a matter of fact, I’m currently building a test apparatus with which I can check several things during driving. Monitoring the crank position sensor is one of those things. As for the idle quality, as it is now - most people would call it good enough. But there is still a little shakiness left, which I expect to disappear after the installation of new injectors. But before I install them I would like to renew the o2-sensor, which I couldn’t do yet. H.D Jun 2014 I have installed the new injectors today. Now problem No. 3 is definitely solved ! The warm engine fires immediately, I don’t have to start it twice anymore. I assume that problem No. 2 (engine stalled at idle several times in the past) is also fixed with the new injectors. But problem No. 1 (the most annoying one) is still not completely solved. The new injectors did not further reduce the idle shakyness. The fuel seems to be atomized more thoroughly though, since with the new injectors the meter for the duty cycle (which represents the o2-sensor emission control) read: at 2500 rpm: 47.5 % +/- 1.5 % (before: 49 % +/- 1.5 %) at 675 rpm: 45 % +/- 1.5 % (before: 46.5 % +/- 1.5 %) That means that the mixture became a little richer. The unchanged rest of idle shakyness leads me to believe that there might be mechanical problems involved. I tried to pin down that hydraulic lifter noise further with a big screwdriver as a stethoscope, and I think it’s coming from the intake valve of the first cylinder. I took out all spark plugs (after 15 minutes of idle) and – besides that all of them didn’t look clean – I saw that the spark plug of the first cylinder was quite wet compared to the others. (see picture!) Then I cleaned the spark plugs thoroughly, plus narrowed the gap back to target, and set the mixture a little leaner to: at 2500 rpm: 49,5 +/- 1,5 % at idle: 50,5 +/- 1,5 % Just a 5° turn of the adjustment screw (counterclockwise) was enough. That reminded me again how delicate the mixture adjustment is! (A duty cycle of 50 % shows that the o2-sensor is fluctuating precisely around a center voltage of 450 mV). Now there is only a little idle fluctuation left. So - maybe because of the failing lifter the intake valve of the first cylinder doesn’t open completely, so that the intake gas can not properly fill the combustion chamber, thus can not be ignited properly, which results in a wet spark plug and remaining idle shakyness !? Or maybe the timing chain is streched a little, so that the camshaft timing is not accurate anymore!? If any of you guys have any feedback about this idea, please let me know! insightful Jun 2014 It does look like you’re getting some oil on that #1 plug. If you put a new set of plugs in, do you get the shaky idle immediately? That black #1 could be the cause of a misfire or the result of a misfire. If the idle is shaky immediately after startup with new plugs, it’s more likely the misfire is causing the fouled plug. Note, I said NEW plugs. Cleaning plugs many times still leaves the ceramic somewhat conductive and likely to misfire. H.D Jun 2014 I can’t get that hydraulic lifter of the first cylinder’s intake valve out of my head – if that is the noisy one, which I think it is. As I already mentioned: if that valve doesn’t open completely because of a (partly) collapsing lifter, maybe the intake gas can’t properly fill the combustion chamber and can’t be ignited properly. The wetness of plug #1 vaporized like fuel. I forgot to smell at it. That spark plug was already less clean before I installed the new injectors 3 days ago. H.D Jun 2014 Okay – I installed the new plugs (NGK “BP 6 EFS”). The cold engine started at the first turn and behaved well. But during warming up with it’s slightly higher idle the engine wasn’t shaky before either. When the engine reached it’s regular operating temperature (after 2 miles) idle was shaky again, however a little bit less than with the old plugs. So – insightful – it’s difficult to tell, whether the new plugs brought an improvement to idle immediately after the first start. Above idle the engine was and is a dream. Flawless up from the moment the wheels start to turn. Now after 15 miles of very modest driving mostly in urban traffic with many red traffic lights, I took the plugs out again to check them and show them to you guys (pictures taken from 2 sides). db4690 – you asked me, whether, while the engine leaks oil, it also uses oil? And insightful also mentions oil as a possible suspect. As you know, I can not see any blue smoke coming out of the exhaust pipe. But maybe there is a little oil involved - more in the first cylinder, less in the others. The plug at the end of the wood is the one from the first cylinder. What do you guys think about the plug appearance? H.D Jun 2014 Maybe the (small) rest of the idle shakyness is caused by: oil getting into the combustion chamber a not completely opening intake valve because of a failing lifter a not very correct camshaft timing because of a slightly stretched timing chain insightful Jun 2014 “But, could I be sure?” I have a gut feeling that the idle shakyness will not be cured by hotter plugs. Why? because it returned immediately with the new plugs before the fouling should have been able to cause it. I honestly don’t know now what’s causing the shakyness. Even a tapping lifter in my experience isn’t accompanied by a miss. Is it a “tap” or a louder “clack”? Certainly getting all the lifters right is a good thing to do. H.D Jun 2014 That’s exactly what I think too: the new plugs were not fouled sufficiently yet to cause misfiring. Immediately after starting the cold engine it’s a “tap”, but not each time. When I go slightly uphill after starting the cold engine (higher load) it’s more a “clack”, but not each time either. When the engine is warm and you keep your ear close to it it’s a “tap”, all the time. H.D Jun 2014 Since the idle shakyness feels a little like misfiring, I can’t get the ignition system out of my head yet. But would ignition related problems not only emerge at idle, but also during other operating conditions, especially when accelerating from standstill? Half a year ago - because of the idle problem - I let a Mercedes mechanic check the ignition system with his old Bosch oscillosscope (which is hardly used anymore), when the engine was hot. He said that it doesn’t look like a brand new ignition system, but he didn’t see anything on the monitor which would cause these kicks at idle. Did any of you guys ever experience an ignition problem that showed symptoms only at idle? db4690 Jun 2014 Yes The engine can be belt to be shaking at idle, due to the misfire That is not always the case on the freeway, going 65mph at 2000rpm H.D Jun 2014 --- Now, the instruction in that Mercedes link says that for my engine the duty cycle at idle should be in the area of 35-45%, which means that the mixture is rich and the o2-sensor fluctuating around a voltage above 450 mV. The opinions about the mixture adjustment are divided. Some Mercedes people I talked to say according to their experience a duty cycle around 50% is better, because than the o2-sensor works around it’s optimal voltage of 450 mV and the mileage is better. Others say that it’s better to go as low as 35%, although that means quite a rich mixture with a little lower mileage, but it’s better for the idle quality, and above idle the mixture would become leaner again by respective input from the ECU to the EHA. --- wesw Jun 2014 HD, you have mentioned before the possibility that your timing chain could be stretched slightly. could it be possible that it is causing your idle shakiness, which then goes away when you put the stress of acceleration on it, causing the slack to transfer to only one side of the chain, while when idling the slack goes back and forth on either side of the sprocket, causing slight fluctuations in your timing? for some reason I really am hoping you get this car perfect. perhaps I m living vicariously thru you? DB? H.D Jun 2014 Thanks guys! – for seeing me through this! This idle issue is quite a project, isn’t it? There are a number of German forums on the web dealing with this idle problem on the M102, M103 and M104 engine. Some people say they solved it by fixing false air leaks, some by renewing things like the distributor, the injectors, the OVP relay, the air flow sensor (potentiometer), the EHA, and several other things. One guy said, that he fixed it by renewing the heat sink paste between the ignition ECU and the surface it is mounted on. Some people in these forums talk about expensive and unsuccessful attempts at Mercedes workshops to solve this problem. But most of these discussions just stop at some point without a solution - at least without the announcement of a solution. One mechanic at a Mercedes dealership who is still familiar with the W124 model - after test driving my car – said: “If it were my car, I wouldn’t mind this little shaking at idle so much. Don’t worry about it, this engine will probably shake for another 15 years.” But for me, shaky idle has no place in a classy Mercedes coupe! H.D Jul 2014 Today I actually wanted to order new hydraulic lifters and valve stem seals from the local Mercedes dealer. But I thought I better quickly open the valve cover and check the old lifters before I spend about 300 $ on 12 new ones. I tried to compress them with a piece of wood (rocker arms on the base radius): none of them collapsed! Then I checked the base position of the camshaft in relation to the crankshaft. When the crankshaft is in ignition TDC of the first cylinder a hole in the camshaft flange must align with a cast cam on the first camshaft bearing cap (see 3rd picture). Looks perfect! So, judging from that, it doesn’t look like the timing chain is stretched! I also checked if there is any lash between the timing chain and the camshaft sprocket: nothing! So the chain elements are not (or hardly) worn either! For a few weeks - as a possible reason for my shaky idle - I have suspected at least one of the intake valves not to open completely due to failing lifter(s). Now I wondered, what the h*** can the “tapping” sound in the valve train be caused by, if not by failing lifters. So I wanted to know what the cams of the camshaft look like, and I disassembled the oil pipe which suplies the cams with oil (it blocks a clear view onto the camshaft). Take a look at the picture of the first intake cam !!! I guess I don’t need many words to describe what I discovered: The cam of the first cylinder is worn off by 1.6 mm (0.063 inch). You see the left edge of the cam is still complete (right below my thumb), and the right edge is only partly still existing. (These are the areas beyond the rocker arm’s sliding surface) The wear of the intake cams: #1: 1.6 mm #2: 1.3 mm #3: 1.5 mm #4: 1.4 mm #5: 0.05 mm #6: 0 mm The wear of the outlet cams: #1: 0.15 mm #2: 0.1 mm #3: 0 mm #4: 0.1 mm #5: 0 mm #6: 0.05 mm So – it’s not failing hydraulic lifters, it’s a worn camshaft, which causes valves not to open completely ! I guess (and now I even hope) that’s what causes: the “tapping” sound the shaky idle ! None of the Mercedes people who listen to my car and drove it, suspected that! So instead of spending 300 $ for hydraulic lifters I may have to spend – I don’t know how much yet – for a new camshaft. I’ll find out tomorrow. I hope that the rocker arms haven’t suffered by these worn cams ! H.D Jul 2014 @ db4690 --- I also talked to an ex-Mercedes master mechanic, who owns his own auto repair shop now, which is specialised on Mercedes. --- And he said the shaky idle could very well be caused by the worn cams and rocker arms. --- 20 days later H.D Jul 2014 I want to give you guys some news about my worn camshaft: I bought the new valve drive parts I talked about in my last posting (camshaft, rocker arms, sprocket, adapter for distributor arm, hydraulic lifters, timing chain - see first picture). Everything looks like good quality. --- Anyway – this wear was the main reason for this thread and it’s title “Mercedes 300CE rough idle”. IDLE ISN’T SHAKY ANYMORE ! --- H.D Jul 2014 @ok4450 “…a vacuum gauge should have showed a problem up like this pretty easily and possibly shortened the process a bit. …” Okay, you’ve convinced me, I add a good vacuum gauge to my shopping list. - https://community.cartalk.com/t/jaguar-s-type-rough-idle/89723 Jaguar s-type rough idle seagates5 Apr 2015 I have a 2001 jag stype v8 with 180k miles. I bought the timing kit and aligned the camshafts correctly but it still idling rough and sounding like a diesel truck. Anyone have any ideas as to what still maybe the problem? ok4450 Apr 2015 Thsoe compression numbers are low. I would suggest that the test be done again using the wet version; meaning a small squirt of oil in each cylinder before it’s retested. If the numbers jump up by a fair amount there’s a piston ring/cylinder wall issue. If they stay about the same then it’s a cylinder head valve issue. --- ok4450 May 2015 I don’t think the engine temperature is going to make much of a difference at all with the compression readings. The jump from 90 to 130 does point to a ring issue. A 130 is not good anyway and 90 is horrible. After listening (or trying to with my poor hearing and tinnitus) I can’t say for sure on the noise. It does sound like multiple causes to me. I’m wondering if the engine is just flat tired and most of the noise is timing chain clatter due to low oil pressure. Oil pressure is what feeds the chain tensioners and keeps the chains snugged up. It seems that I hear a rod bearing rap in there also (which could influence oil pressure) but I’m not certain on that. To be honest, I think that motor is a goner. --- - https://community.cartalk.com/t/cylinder-head-and-head-gasket-replacement-for-my-honda-civic/72853/6 Cylinder head and head gasket replacement for my Honda Civic TJ_craftsman Jun 2012 I have a 1997 Honda Civic that I was given by an elderly neighbor’s daughter after the elderly lady went to the grocery and ended up 100 miles away when she could not figure out how to get home. The car was smogged at the beginning of the year but when I got it ran very rough and the temp went nearly to overheating on the drive home when I was stuck in stop and go traffic. I found the radiator fluid level low and an oily residue inside the radiator water bottle. I took it to a mechanic to check it out and was told it had a blown head gasket and maybe worse. --- It’s hard to know but I am guessing that the engine was damaged during the 100 mile road trip due to low coolant level. --- Any suggestions on if there is a way to detect if I could be facing bigger issues like failed bearings? ok4450 Jun 2012 There are a number of tests that should be performed before a definite head gasket diagnosis is given. A compression test is the first one with a vacuum test (which may not be definitive), hydrocarbon test, cooling system pressure test, etc. If you do the wet test (meaning a squirt of oil into each cylinder as you retest it) it can be assumed if the rings are bad that the readings will take significant jump upwards; say 25 PSI or more. If the readings do not go up or go up very slightly then that would point to a head gasket breach or valve issue. --- (Regarding a potential valve issue, valve lash should be inspected every 30k miles and adjusted as necessary. Seldom is this done; unfortunately. If a valve tightens up this can lead to rough running, cylinder head valve damage, and even overheating due to engine strain. If your wet test shows a valve problem then pop the valve cover and check the lash for tight valves.) Hope some of that helps. TJ_craftsman Jul 2012 Hello all, Just to let everyone who made a comment know the outcome of my engine adventure here’s the conclusion. I decided to go for an engine swap with a rebuilt engine to replace my problematic engine. --- They found three things wrong at least with the engine. They found a crack in the cast iron cylinder liner between cylinder two and three, a faulty distributor, and an arcing spark plug wire. I did not get a report on the blown head gasket... --- - https://community.cartalk.com/t/low-idle-when-engine-is-warm/176628 Low idle when engine is warm GVe1321_175095 May 2021 I have a 2003 Toyota Camry SE with a 2.4 4 cylinder. When I go to the store and come back to my car to start it up, it idles low and rough for around 30 seconds and then it slowly creeps back up. This only happens when my engine is warm and I start it up. Does anyone have any clue what could be happening and what I can do to fix this? Thanks! GVe1321_175095 Mustangman May 2021 Yes the check engine light has been on for quite some time. It’s throwing p0441, p0442, and p0446 evap codes. Do you know any possible causes for these codes? I’d like to fix it rather than clear the codes. VDCdriver May 2021 --- Yup! A disconnected vacuum hose can lead to those 3 codes: https://www.bing.com/videos/search?q=po441&&view=detail&mid=05AD4C20D86A8247635C05AD4C20D86A8247635C&&FORM=VDRVRV --- - https://community.cartalk.com/t/98-maxima-runs-rough-once-it-warms-up-doesnt-idle- well/83947 98 Maxima runs rough once it warms up/doesn’t idle well TheMisses2013 Feb 2014 My 98 Maxima won’t idle without dying, it sputters when you accelerate, and it tries to die while coasting. I’ve changed two O2 sensors (AutoZone gave me code for bank 1 sensor 1 & 2) changed spark plugs, tried fuel injector cleaner, oil change, and cleaned MAF sensor & checked wiring. It;s still spitting out black exhaust. Although after changing the O2 sensors it quit for about a day or two, but started again (I’m guessing the other sensors need to be changed to) But the main problem is once it warms up, it really runs like crap, and is a major gas hog. I’m getting about 12 Mpg. HELP!!! lol cigroller Feb 2014 “code for bank 1 sensor 1 & 2” is way too vague. Do you recall the specific code numbers? (e.g. P0171 maybe? P0172?) Lots and lots of codes. (If you’d like, go here. First do a search for “sensor 1” and then do a search for “sensor 2.” You’ll quit before long). I’ll guess this - I’ll guess it was a code that indicated that you are running rich (e.g. P0172) - because it sounds like you are. And I’ll further guess that you let the Autozone person help you fall for the trap that codes tell you that sensors are bad? (Sometimes, sure). Anyway, I’m guessing that the engine light is back on and even if it isn’t have it scanned for codes again. It sounds like the trouble begins after the car enters closed loop or should be entering closed loop, and I would check the coolant temperature sensor. You changed the plugs. How are the wires? I would also check the fuel pressure and fuel pressure regulator. But having codes would help. If you can get it on a scantool that does live data a peek at the fuel trims would probably say a lot. cigroller Feb 2014 “I just remember it said something about the sensors being bad” That’s what I was trying to say - there are no codes that tell you that any sensors are bad. All a code ever tells you is that the computer sees something [consistently enough] out of spec. The actual cause for what the computer sees is always TBD by a human. You will hear all sorts of things. That’s because a) lots of people don’t know what they’re talking about (leave open the chance that that is self-referential) and b) people don’t have the info they need. There are 101 things that will make a car run poorly. Intelligent testing is how to get the 101 down to 1. That often starts with diagnostic codes. So get the codes read again, but this time don’t buy anything. Just write down the “Pxxxx” number and post it. When you do that report more about the car. How many miles are on it? What is the overall state of maintenance & its history? Not “oil changes” - but all of that stuff the owner’s manual lists. So far we know the plugs aren’t that old. George_San_Jose1 Feb 2014 The most common DTC reading can usually done with the engine turned off. It just reads the codes that have been stored in the computer’s memory. Might be codes from yesterday, or two weeks ago. Live scan means they hook a scan tool up while the engine is running and look at various measured engine parameters and how they change over time, like as the engine warms up, they’ll look at parameters like fuel-trim which can be diagnostic in a situation like this. Fuel trim is how much extra gas (or reduction in gas) is required to be injected to achieve the required O2 reading, beyond what the computer thinks would be required for that situation. Since the problem occurs once the engine is warmed up, this would be consistent with an air/fuel mixture problem. The O2 sensors are the primary method of controlling air/fuel mixture, and they don’t start working until the engine is warmed up. Before that, they computer uses it’s open-loop parameters to calculate fuel injection rate. In your case the O2 sensors, once they come online, they may be saying there’s too much O2 in the exhaust, so it thinks more gas is required. But it is possible the O2 may be coming from an exhaust leak, not that there’s too much O2 in the intake manifold. When the computer attempts to correct for too much O2 in the exhaust, it injects extra fuel into the intake manifold, which makes the combustion mixture too rich, causing poor performance and poor mpg. You might consider asking your mechanic to do a fuel trim measurement. TheMisses2013 Feb 2014 I’ll have to double check then LOL. Although when we changed them, they were clogged & black. Also, when my husband was taking stuff apart, I don’t remember exactly what it was, but it was up by the accelerator somewhere, some black piece he took off, it had tiny little pieces of what looked like charcoal in it? The car has 262K miles on it…When I got it, there was no maintenance records, nothing. just that the person I bought it from only purchased it 5 months before… But as soon as I can get the codes read again, I’ll do that! George_San_Jose1 Feb 2014 That gadget with the black stuff on it might have been the idle air control valve, or it might have been the throttle body. No harm done to clean them. Probably did some good. But it sounds like there is at least one more problem remaining. cigroller Feb 2014 “when we changed them, they were clogged & black” I assume that is about the O2 sensors. They were clogged and black for the same reason you have the smoke out of the tailpipe - you’re running rich, or burning tons of oil. Do you have to add oil a lot? Anyway, as George mentioned the O2 sensors report to the computer on the air/fuel mix. A lot of people assume that a code that says a sensor is reporting rich/lean means the sensor is bad. Meanwhile, the sensor is doing exactly what it’s supposed to do. So changing it is shooting the messenger. You said the car is running rough and getting lousy mileage and blowing smoke. All of that adds up to running rich - so the codes probably say about the same thing. So then you look for reasons there is unburnt fuel blowing through the exhaust - fuel pressure problems, fuel injector problems, spark problems, “information” problems (like a bad coolant temp sensor), etc. P.S. running rich can gum up the O2 sensors, so you may have needed them anyway. But if the new ones get gummed up… TheMisses2013 Feb 2014 Yes, the O2 sensors were clogged. And I checked the slip, the codes were P0134 & P0154. The oil level is usually fine, The part w/ black stuff, it wasn’t ON it, it was IN it. Like tiny little charcoal-like pellets rolling around inside. cigroller Feb 2014 Have the code read again and report back. If they are the same, then note that those codes are about the circuit not the sensors. The sensors are part of the circuit - the rest of it has to do with the wiring, including the connections at the computer. Both codes say that the computer see nothing from those sensors. So, the first thing to do is check the wiring. If you go to Autozone’s website and register an email address you can plug in the car’s info and get access to wiring diagrams to help with that. But the car is running very rich. This could have something to do with the O2 sensors since they are needed for the computer to do the fuel / air mix. But it could also be other things causing the rich running - and then gunking up the sensors again. It’s a non-virtuous cycle. For running rich go back to my earlier notes - spark plug wires, fuel pressure and fuel pressure regulator, coolant temperature sensor… The car isn’t running cool is it? As in, not getting all the way to temp and maybe producing very little heat? TheMisses2013 Feb 2014 Alright, I’ll try that. Thanks :slight_smile: No, temp runs normal, right in the middle. There’s also issues with it idling low. We’ve raised the idle some, and that helped w/ it dying, but not for long. It always seems to get loosened up. George_San_Jose1 Feb 2014 Might be worth it to have a compression test done too. A burned exhaust valve can allow unburned gasoline directly into the exhaust steam. That would usually show up on a compression test. Tester Feb 2014 The problem might be with the fuel pressure regulator. http://www.rockauto.com/catalog/moreinfo.php?pk=47110&cc=1316803 10 If the fuel pressure regulator developes a leak at the diaphram, the engine will draw in excess fuel causing a rich condition. The fuel pressure regulator is located on the fuel rail. Start the engine and let it idle for thirty seconds. Shut the engine off and remove the vacuum hose from the regulator. If gas leaks out of this connection replace the fuel pressure regulator. Tester TheMisses2013 May 2014 It’s been a while, but I finally managed to have the CE light checked again. The codes are: P0154, P0134( this is one of the sensors we previously changed) , P0100, P0300, P1320… insightful May 2014 Have you checked the fuel pressure regulator per @Tester? insightful May 2014 You’ll be money ahead to take it to a good mechanic and authorize at least an hour of diagnostic time. It’ll be the best $100 or so you ever spent on this car. TheMisses2013 May 2014 Probably so! cigroller May 2014 You didn’t list out all of the codes. This doesn’t help. I’m going to assume that you have a bad wiring harness someplace. One of the things this is doing is killing the signal from your upstream O2 sensors (P0154, P0134). Once the car warms up the computer needs these signals to do the air/fuel mix. It is also messing with the MAF or MAF signal (P0100). The result is that the car will run like crap once it’s warmed up and perhaps misfire a lot (P0300). If you had actually listed all of the codes, it might be easier to see a picture forming. For now, when you do take it in, no codes refer to sensors. It’s completely impossible. The only way for the computer to “see” a sensor is via wires. Codes refer to circuits. You probably have a problem in one or more. Either that or you’ll be looking at a new PCM. Whatever you do, don’t let someone just start throwing parts at the thing. tardrex May 2014 I just had a very similar problem as yours with my 93 maxima, http://community.cartalk.com/discussion/2297944/1993-nissan-maxima-rough-idle-horrible-gas-milage#latest 17 I replaced several parts at the same time so I cant say for sure which part,or parts, were causing the problems but I suspect that the MAF was the main culprit,because when I disconnect the new MAF, while the car is running,the engine exhibits many of the same symptoms that it had with the old MAF installed.The old MAF "looked" fine so I didnt replace it originally I just cleaned it and put it back on. The check engine light never came on and there were no codes which made finding the problem more difficult.Anyhow I hope my experience can be of some help to you and shed some light on the problem your having. - https://community.cartalk.com/t/1993-nissan-maxima-rough-idle-horrible-gas-milage/84829 1993 nissan maxima rough idle horrible gas milage tardrex Apr 2014 Greetings, I sure hope hope someone can help me. my daughter has a 1993 maxima SE (3.0 DOHC) that ran ok until one day when she left work and started the car it was running very rough (missing and sputtering). She had the car towed here and I looked it over,it had a lot of visible problems which I have fixed (cracked coil packs,leaking valve cover gaskets, filthy fuel filter,clogged pcv valve, oil saturated air filter,spark plugs burned down to nubs etc, I replaced all those obviously defective parts) but the car still idles very rough,idles too low RPMs(400-500 rpms),exhaust smells like raw fuel and it only gets 5 miles to the gallon on my last test drive. I removed the intake manifold to get to the rear fuel injectors to see if they might be stuck open and leaking.The car had been sitting for about 5 days with the battery disconnected and when I removed the first injector there was no fuel in the injector or the rail and no pressure in the rail. I left the injector out overnight and the next morning there was fuel all over the top of the engine and in the fuel rail. I put the injector back in and unbolted the rail,I reconnected the battery and turned the key to start the fuel pump.I waited for about 3-4 minutes and did not see any fuel leaking from the injectors.I turned the key off and removed it from the ignition,disconnected the battery and bolted the fuel rail back down.I again removed one of the injectors and there was no fuel in the injector or the rail and no pressure in the rail.After about 2 minutes, with the key out of the ignition and the battery disconnected,I saw fuel start filling the rail and the injector port, so I quickly put the injector back in. I`m thinking the next step would be to replace the fuel pressure regulator and recheck the injectors for leaks.Am I on the right track here with the pressure regulator? What could be causing the car to suddenly start acting this way, my daughter said the car ran fine on her way to work ( although I hardly think it could have been running “fine” with cracked coil packs,clogged air filter,worn plugs etc) Any suggestions will be greatly appreciated. jesmed1 Apr 2014 I would check to see if the timing belt/chain jumped a tooth. That would explain a sudden rough running and poor gas mileage due to unburned gas because the valve timing is off. Given the apparent lack of maintenance, a loose timing belt/chain and/or weak tensioner would not be at all surprising. tardrex Apr 2014 Thanks for replying. That would be my worst nightmare,but I did briefly consider that might be the problem. Since it has DOHC it has 3 timing chains which increases the chance that one of them might have slipped. I suppose the easiest way to check that is to remove the valve cover on the number 1 cylinder and handcrank the the crank shaft until number 1 is at TDC then look at the camshaft to see if the valves are open or closed? jesmed1 Apr 2014 But what if that bank of valves is still timed correctly and it’s the other bank that jumped? You may have to pull the chain cover and check all the alignment marks. ok4450 Apr 2014 Maybe the fuel pressure regulator is leaking. That could explain the poor running, bad fuel mileage, raw gas smell out the exhaust, etc. The car is 21 years old and the rubber diaphragm in the regulator could easily have given up. BustedKnuckles Apr 2014 Have you checked the fuel pressure, yet? This simple test can eliminate a lot of the guessing. Fuel pressure way above spec is usually a faulty regulator. Fuel pressure good usually points to either bad injectors or a possible faulty ECU. tardrex Apr 2014 I dont have fuel pressure gauge,Ill get one this weekend and check the pressure and the timing chain this weekend also. One other important thing that I failed to mention is that the check engine light has never come on,so Im assuming that whatever is causing the problem is something that is not monitored by the ECU,which is why I havent checked any of the sensors or anything else that is monitored by the ECU, I`m assuming they are all working correctly and will check them as a last resort. Im really baffled as to why there was no fuel or pressure in the injectors or the fuel rail until after I removed the injector.The battery was disconnected so the fuel pump couldnt have been running so what was forcing the fuel up and into the fuel rail only after the injector was removed? BustedKnuckles Apr 2014 A '93 model year car uses an ODB-I system, which is not very sophisticated. Basically, it will only set a code if it cannot read a sensor, but lacks the ability to determine if the signal from the sensors is considered reasonable or reliable. '96 and newer cats use ODB-II, that has a lot more ability, including mis-fire detectors that ODB-I doesn’t have. So, working on pre-'96 cars requires a lot more old-fashioned diagnostic work to be done that newer cars. tardrex Apr 2014 Thanks for that info I didnt know that. so, the cam position sensor/s could be malfunctioning which could cause symptoms similar to a slipped timing chain and that wouldnt necessarily cause a fault code? When I check the timing chain if it is ok and hasnt slipped maybe Ill focus my attention on the cam sensor/s db4690 Apr 2014 @tardrex‌ When you get that fuel pressure gauge, bear in mind that your car almost certainly does NOT have a fuel pressure test port. As such, you’ll need to tee into the system, so to speak. Make sure that fuel pressure gauge set has the adapter you need cigroller Apr 2014 It does seem clear that you are running very rich - or there is a timing issue. When you had the injectors out, I’m not sure your check for leaking was complete. If the rail had gone completely empty and was at zero pressure, in order to fill and pressurize the rail you would have needed to cycle the key on and off a whole bunch of time. If the car isn’t cranking/running, the pump only cycles on briefly and cycling once won’t fully repressurize the rail. (Once you get your hands on a pressure gauge you can certainly verify/check). The part about the fuel rail filling with the key off and battery disconnected is just plain odd. I don’t know what to make of it. Either way, I would leave leaking fuel injectors on the table. The pressure regulator is easy to check by just pulling the vacuum line and checking for liquid fuel - there shouldn’t be any. The car would need to have been running just prior to this. I would also do a basic check of the coolant temp sensor. This can easily be done with an ohmmeter since those generally just work by resistance - lower when cooler / higher when hotter. You’d need to dig up the resistance specs someplace. Even on OBDII systems the error detection is not perfect. There is a lot of tolerance built into the programming - random errors / blips flow around the systems regularly. Most of them are random little blips. Many things operate within a given range. So for most of the monitored systems, its not as simple as “error/no error.” The tolerances for error, then, means that things can be out of spec enough to cause problems, but that it hasn’t triggered the PCM’s programming for calling it an error. tardrex May 2014 Today I pulled the valve covers and the timing chain covers,turned the crankshaft by hand until #1 was at TDC,the timing marks lined up correctly and the chains were nice and tight.When I removed the rear valve cover I did smell gas,but the smell went away pretty quick and I didn`t see any gas. I removed the connector from the coolant temp sensor and saw a lot of green corrosion.(I could just clean it but they are cheap so I`m going to replace it and clean the connector) I pulled the fuel rail up again and cycled the key on and off about 25-30 times,to build pressure in the fuel rail, and none of the injectors showed any signs of leaking.After I bolted the rail back down I removed the fuel pressure regulator to check if there was pressure in the rail, there was pressure but I can`t say for sure how much. I got new gaskets (valve cover,intake,egr gaskets) some new vacuum hoses (all of the hoses are brittle and some of the hoses I removed, to take the intake off, broke.) and a coolant temp sensor on Ebay.I going to go ahead and put everything back together next week. I might get a new O2 sensor too if I find one cheap on Ebay. After I get it all back together I`ll get a fuel pressure gauge and start checking some other things too. ( TPS,MAF,IACV,Cam position sensor,fuel pressure regulator) I only found 1 oxygen sensor on the car (screwed into the side of “Y” pipe under the car) I also noticed that the car doesnt have a catalytic convertor. There is this braided wire collar type thing (like this: http://s.ecrater.com/stores/36412/4e3bc3904245c_36412n.jpg) welded onto the "Y" pipe and then just a straight exhaust pipe running to the back of the car.I assume that someone didnt want to pay $1 million to buy a new catalytic convertor so they removed it and put a straight pipe on. We dont have to get emissions tests where I live so im not going to bother putting a catalytic convertor back on unless it`s needed to make the car run properly again. ok4450 May 2014 You could have removed the vacuum line from the fuel pressure regulator to see if there was any gas in it. A vacuum can also be pulled on the regulator to test the diaphragm. tardrex May 2014 Just to update y`all on the situation, I replaced the O2 sensor,temperature sensor,the MAF,PCV valve, and a used TPS, put the intake manifold back on,with a new gasket,reconnected all the hoses and wires etc, and it runs good now. I replaced them all at the same time so I dont know if it was just one of those things that was malfunctioning or a combination of 2 or more of them. It idles smooth at 700 RPM, no missing, and theres no fuel odor coming from the exhaust. I have a new problem now, I noticed a puddle of oil (at least a coffee cup full or more of oil) by the inside of the front passenger tire. I asked my daughter if she noticed any oil leaks when she had the car and she said: oh yeah it leaked a lot but I would just put a quart of oil in every 2-3 days and some stop leak now and again and it was fine. All you can do is roll your eyes when someone says that. The leak is on the passenger side of the engine where all the belts and pulleys are, I guess Ill check the oil pan gasket,oil filter and crank seal to see whats leaking. Its odd that I didnt see any oil puddles before now, maybe all that stop leak she put in there finally burned up or leaked out? Hahahaha This is getting to be a never ending project. ( Total expenses so far for parts is about $250 +/- $10, new coil packs for $5 each, new MAF for $20, gotta love Ebay) 5 years later cngarch_144871 Nov 2018 Try the crankshaft sensor down neat the oil filter. It tells the timing of the engine to the computer. PvtPublic Nov 2018 5 years late and obviously didn’t even read the whole thing. Running problem fixed. - https://community.cartalk.com/t/88-ford-van/88534 88 Ford Van mad_cowboy Jan 2015 Hello to all , this is my first time, of course I am having problems with my 88 ford half ton custom van with a 5.0 engine. Problems being the key word, I'm not sure if it is one thing causing the problem. I've had the van for about a year and a half , so I kind of like it. Being old but not badly maintained it is still a decent ride, in other words I expect it needs money thrown at it, just where and how much is the question. My worst problem is that it is not idling properly . This just started recently , It was running hot on the temp gauge and leaking water so I replaced the thermostat (Quite the pain till I learned the trick) and replaced most of the leaking hoses. I dont think this caused the problem, I also replaced the rotor and cap , the cap was pretty wasted, and fairly old like the spark plugs , I'd replaced a few months back. I'm not sure if my problem is electrical or vacuum , it does have duel gas tanks and a bunch of things to go wrong there. On the highway it seems to run ok but at a stop it starts idling erratically and then dies. It starts right back up, but I smell like a bad gas smell. My check engine light comes on if I'm driving slow but goes off at about 30 . Another clue is that it idles worse, higher when I run the heater. It almost runs ok with the heater off, perfect for winter driving. I'm basically looking for things to try next. Or first would be best. I've thought of getting the things that could be causing the problem at a junk yard and replacing them until I notice a difference. I know of the IAC and the ERG maybe , also read of a temp sensor on the throttle body? It needs some other things like a power brake booster that leaks air. I'm not very technical but willing to do the homework. Any thoughts will help and thanks for letting me post here. Tester Jan 2015 One trick to try if it’s the IAC valve causing the idle problem on a Ford is, while the engine is idling at temperature, take the handle of a screwdriver and rap on the IAC valve. If the engine idle speed changes the IAC valve is bad. Tester mad_cowboy Jan 2015 thank you I will try that. Yosemite Jan 2015 Most auto parts stores will read the codes for you for free. They will be in a PXXX format and post those code numbers here for us. Then we may have a little more info to give you a better answer. Yosemite BustedKnuckles Jan 2015 Yosemite, it’s an '88, so it’s OBD-I. The test connector needs to be jumped and codes read by reading the blinks on the CEL. I’m wondering if the fuel injectors are dirty. Reading the spark plugs can tell you if an injector or two are acting up. insightful Jan 2015 “It needs some other things like a power brake booster that leaks air.” Fix that first. It may solve the idle problem. Howie32703 Jan 2015 If your power brake booster is leaking air as you said it creates a vacuum leak and will cause a low idle, but less pronounced at higher speeds. Has anyone messed with the throttle body idle adjustment screw ? This is used to set the base idle with the IAC disconnected and should not be messed with after setting it up. Also an EGR valve not closing all the way can cause your symptoms. You need to pull the codes just using a paper clip. You have to place this between connecting points on 2 female connectors located near the driver side firewall…These maybe located elsewhere as I am going by my 89 5.0 in my stang. You can also check the TPS by using a simple voltmeter. Caddyman Jan 2015 1988 is when they were converting from carburetors to fuel injection…The emissions systems used back then can be a nightmare with the technology changing every 6 months… keith Jan 2015 Runs good cold but not hot, often that points to the ECTS engine coolant temperature sensor. Best to get the codes first though. mad_cowboy Jan 2015 it still idles erratically and dies , now though it seems to do it mostly when it was cold. Tomorrow I’m going to take it to work , see if it makes it. It’s a mess but not as bad, and hopefully some of the things I replaced would of eventually went bad or were due anyway. Thanks that makes sense on the gasket, on this one to really clean anything you have to take the iac body off the throttle body, At the 2 screws there was like a valve , I depressed the pin in it and sprayed in it but I don’t think it changed anything. wesw Jan 2015 you have to clean inside the hole it came out of also. I just sprayed the crap out of everything and brushed or wiped it all with a shop rag. there were dark deposits on the plunger and in the hole it came out of. I removed all crud and had good results mad_cowboy Jan 2015 when I took the iac apart there was no crud , it looked pretty clean Rod-Knox Jan 2015 Re the IAC, the shaft can get gunked up and fail to move. I have poured a 1 to 3 mixture of amonia and water into IAC valves and stirred it around, dumped and repeated several times often with good results. And more often than not the gasket was left on undamaged. This was just preventative maintenance on several models that tended to have problems with idle quality. keith Jan 2015 If your throttle position switch has two parts, one a variable resistor and the other a switch that detects throttle off and wide open throttle, check the switch side and make sure that the contacts are making when the gas pedal is not depressed and the contacts make for WOT. If they aren’t making, it could be a bad switch or someone has adjusted the throttle stop screw to the point that the switch doesn’t make anymore. If this switch doesn’t make, the computer does not take over to control the idle. People think the IAC isn’t working, but it is simply not being commanded to work. - https://community.cartalk.com/t/rough-idle-cycling-when-cold/109867/16 Rough idle (cycling) when cold thegreendrag0n Dec 2017 not necessarily my Nissan experience will help, but upon cleaning a throttle plate (which you mentioned earlier), you are supposed to perform the “idle self-learn” procedure for my Pathfinder, the procedure was: start from warm engine shut down and disconnect MAF start engine and let run for ~5 seconds, until you get CEL stop, reconnect MAF turn ignition on, do not start, clear MAF code, turn off start engine and let it idle for 20+ minutes, do not touch the gas pedal drive as usual after that you can find more info at nissanhelp.com 5 or relevant infinity forums (if any) George_San_Jose1 Jan 2018 Think positive, the re-learning on the IAC and re-programming the MAF sensor may have fixed it. If not, rough idling when cold suggests the mixture is too lean. Some combo of too much air nor not enough gasoline entering the cylinders. That could be caused by a vacuum leak, air induction system leak, low fuel pressure, faulty engine coolant or intake ambient air temp sensors, clogged injectors etc. L_J_Pressman Jan 2018 We finally to got to the bottom of this problem after these many weeks: "After repairing my buddy’s 2000 Max for the exact same problem, I would be willing to bet on the o-ring gasket for the plastic upper intake manifold. BTW, it also had the new MAF, ECU reprogram and six new coils that helped but did not totally fix the issue. An air leak is created by the old brittle gasket where the plastic upper manifold meets the aluminum lower manifold. Gets better when the engine is warmed up. The parts man at my dealer has seen several of these, and recommended this as a fix.The updated part number should be in the database at your dealer. Sorry I don’t have it in front of me, but the dealer should have it." Thanks to everyone for their help in troubleshooting. I have passed on the word to my ‘car talk’ and the Infiniti mechanics. L J Pressman George_San_Jose1 Jan 2018 OP … your post above is a little unclear. Is it solved now? Was it in fact caused by a vacuum leak due to a faulty upper intake manifold gasket? 10 days later L_J_Pressman Jan 2018 Yes, that O-ring was the problem. I have not had any problems since. George_San_Jose1 Jan 2018 Glad to hear you are back to a smooth running engine. Good for you for sticking with it. - https://community.cartalk.com/t/e36-randomly-dies-on-cold-start/188056 E36 Randomly dies on cold start Kalcho Dec 2022 VID_20221221_160447.mp4 - VEED 12 – Here is a video of the problem. When I start the car cold in the morning It shuts down in random time periods and it shakes a lot. I have to wait for at least 5 to 10 minute to drive it so that I doesn’t shut down while I drive. I wonder if it’s a sensor or something more serious. Manolito Dec 2022 The first thing to check is the air duct from the air filter to the throttle body. Those get old and crack, and the car has more trouble compensating for the leak when it is cold. Vacuum leaks are another possibility, but those will generally cause a rough idle and a check engine light when the car is warm. --- George_San_Jose1 Dec 2022 Assuming this car is OBD II tech, ask your shop for a fuel trim test. If there are engine air or exhaust leaks, good chance the problem would show up there. I wonder if it’s a sensor or something more serious. Suggest to approach this by first determining what’s causing it. It could be a lot of things, but replacing stuff on a guess gets expensive very quickly. And can end up with the car in worse shape than when you began, b/c good stuff gets replaced with aftermarket bad stuff. - https://community.cartalk.com/t/1989-dodge-dakota-runs-bad-when-cold/150441 1989 Dodge Dakota - Runs Bad When Cold henrywalley Oct 2019 when engine is cool below 70 deg it runs real bad like two cyl, and when it warms up it run’s real good? davepsinbox_157004 Oct 2019 My top of the head guess would be a fuel injection issue. The fuel mixture might be off slightly when the engine is cold. Older vehicles had chokes for that purpose but newer ones rely on computers. - https://community.cartalk.com/t/03-ford-focus-occasionally-runs-rough/78517 ‘03 Ford Focus occasionally runs rough Bike_Guy Apr 2013 My son drives a 2003 Ford Focus with 183,000 miles on it. At random times when he starts the car, the engine runs very rough at idle speed but when he drives away, it runs fine until he slows for a stop sign/turn, etc. and the engine is at idle speed again. When this happens, the engine runs so roughly, that he loses vacuum to the brakes and his brakes stiffen dangerously. The car may not do this at all for a couple of weeks of driving, and when it doesn’t do it, it runs beautifully. Also, it only runs like this if it does it from start-up; it never idles roughly in the middle of a drive in which the car started normally. I have changed the spark plugs and wires, PCV valve, fuel filter, and air filter, but it still goes through this about once a week. I bought the car used just a few months ago and it had just had the valve cover gasket changed because the valve cover was leaking. I don’t think this plays a role in the above-mentioned problem but thought I would add this info if it helps. Thanks common-sense-answer Apr 2013 Look At All Those Clamps On The Rubber Boots Of The Intake Manifold. Make Sure The Clamps And Boots Aren’t Loose, Mis-positioned, Or Separated. Problems have been found in this area on 2003-2004 Ford Focus models and can cause problems, including rough idle, especially on cold starts. Ford’s got a Technical Service Bulletin TSB 07-10-7 that addresses this issue. CSA Tester Apr 2013 The problem might be caused from a dirty/defective Idle Air Control valve. The next time the engine’s idling rough at operating temperature, locate the IAC valve on the throttle body, and tap on it with a handle of a screwdriver. If doing this causes the idle speed to change replace the IAC valve. Tester Jims2011FordFocus Apr 2013 I’m not sure if this is related, but my 2011 Ford Focus would idle rough (engine vibration), when it was cold. It would last for several miles, then quit. The dealer decided to change out the front motor mount. The rough idle (engine vibration) has quit for now - however, the weather has warmed up since the change out, so I’m not 100% convinced that it is cured, so I may have to wait till next Fall. (Oklahoma) What I learned from the dealer is that the motor mounts are fluid filled, and can rupture / fail. Mine didn’t, but the cold weather may have made them more stiff, therefore allowing normal engine idle to vibrate in the car cab. - https://community.cartalk.com/t/rough-idle/64796 Rough Idle radsaxon May 2011 I have a 2001 Ford Escape, and when I start it for the first time of the day, it idles really rough, and way below 500RPMs (to the point where it almost stalls). After about 10 minutes, when the car is all warmed up, it runs smoothly, as if there was nothing wrong with it. The only conclusion I can draw is that it is temperature related, but I can’t figure out exactly what is causing the issue. Any suggestions? PS: This happens on the driest or wettest of days, so moisture doesn’t seem to be an issue. Caddyman May 2011 The ECM is supposed to take temperature signals from the air intake and engine and use those to adjust the fuel mixture a little richer during “warm-up”…If this is not happening, for whatever reason, the engine will run rough until it warms up… - https://community.cartalk.com/t/could-ecu-act-up-intermittently-causing-high-idle-any-other-ideas/191366 Could ECU act up intermittently causing high idle? Any other ideas? Jahagafut_185280 Jun 2023 I’ve got an 03 Buick Lesabre, 3800 Series II, predictably after an hour of driving the idle starts to get high, it used to go to 3500 but I’ve since replaced the parts I’ll list at the end and it now hangs out around 1800. Sometimes I can sit parked and it goes back to 700 for a minute. If you let it sit turned off it will go back to 700 but quickly start idling high again unless its sat long enough to cool down. --- Tester Jahagafut_185280 Jun 2023 Try unplugging the power steering pressure sensor,(same as a pressure switch), to see if that stabilizes the engine speed. ... yourmechanic.com Tester Jahagafut_185280 Jun 2023 I will give this a try. I did notice this morning when parking the power steering seemed to stop for a few seconds then return Mustangman Jun 2023 You didn’t tell us the shop you used actually captured live data… That just reinforces their suggestion to replace the throttle body. Why do you think that is not a valid suggestion? Again… hands on the car vs random internet forum folks who’ve never even seen your car. NYBo Jun 2023 Did you spray the ends of the throttle plate shaft? Those are wear points. TwinTurbo Jun 2023 Not sure it’s done much anymore but the throttle shaft wears out the bore in the throttle body and creates an air leak. Back in the day, it was fairly common repair to bore out the throttle shaft holes and install bushings to restore the seal between the shaft and throttle body. Probably more cost effective today to replace the assembly… TwinTurbo Jun 2023 You can try wiggling the shaft. If it’s worn too much for the spray to be effective, it will be fairly obvious. If it seems tight in the bores, then try spraying the places on each end where the shaft enters the throttle body as NYBo suggested. See if the RPMs are affected by leaks around the shaft… - https://community.cartalk.com/t/could-ecu-act-up-intermittently-causing-high-idle-any-other-ideas/191366/31 Could ECU act up intermittently causing high idle? Any other ideas? George_San_Jose1 Jul 2023 Idle air schemes vary greatly, car to car and over the years. Can’t speak to OP’s car, but on my Corolla, there are several pathways for air to enter engine at idle, even though IIRC the main throttle-body butterfly valve (cable operated by gas pedal) is 100% closed at idle. air bleed screw. bypasses butterfly valve, manually operated, used (by me) to set warm idle rpm during tune-up. idle air control gadget. bypasses butterfly valve, controlled by thermostat-like action by coolant temperature, 100% closed when coolant warm, but opens as a function of coolant temperature, lower coolant temperature, more open. It is possible to completely block this path without affecting any of the other idle-air paths w/ my Corolla’s configuration. VSV. Vacuum switching valve, misnomer b/c not really related to vacuum, air-valve, electric solenoid activated, allows air path directly into intake manifold, essentially bypassing butterfly valve, controlled by ECM, activated to open by ECM (or associated electronics) when headlights or rear window defrosters are turned on, used to compensate for alternator load on engine. Power steering pump VSV. Another misnomer, not related to vacuum, air valve into intake manifold, actuated by power steering pump when power steering pressure is high. Used to compensate for add’l load on engine by power steering pump. George_San_Jose1 Jul 2023 --- Every car uses its own CEL-deciding algorithm. One thing is certain, when the CEL turns on, it annoys the car’s owner. There seems to be a tendency among the manufacturers to delay turning it on until the problem is confirmed over several drive cycles, avoids turning the CEL on due to a temporary glitch. --- George_San_Jose1 Jul 2023 Engines that idle at too high rpm or that fail to crank the engine with the key in “start” are two of the most annoying car problems imo. - https://community.cartalk.com/t/cam-sensor-red-herring/75772 Cam Sensor Red Herring? DDT Nov 2012 I drive a 97 Ford Thunderbird 4.6L V8 with 135K miles. I’ve got a check engine light that gives a cam sensor code. The car also idles rough, and recently stalled on me when I went to pull away from a stop. The mechanic put a new cam sensor in it, only to have the check engine light return (immediately–same code), and it still idles rough. I’m also pretty sure that I’ve tried replacing the cam sensor before, in the last 6 months or so. Before I put myself at the mercy of the Ford dealer (as my mechanic recommended), I’d like to have some idea what I might be dealing with. When is a cam sensor problem not a cam sensor problem? ok4450 Nov 2012 There’s also at least a decent chance this rough idle is not related to cam sensors at all. I can’t be specific as there are too many loose ends but just wanted to point that out. Does the car seem to run and drive out fine going down the road? ok4450 Nov 2012 Connecting a vacuum gauge might help. It’s cheap, easy to do, and any anomaly that exists should steer the diagnostics in the right direction. DDT Nov 2012 @ok4450 - it runs fine going down the road. It’s only rough when idling in Drive, like at stoplights. Pop it into Neutral, purrs like a kitten. Put your foot on the gas and pull away, it runs nice and smooth. ok4450 Nov 2012 While it’s possible a cam sensor could do this I suppose, if the car were mine I would be looking at a vacuum problem, Idle Air Valve problem, or a slightly lowered engine idle speed. Those things are kind of mingled and that’s why my suggestion about a vacuum gauge. DDT Nov 2012 Hm. I had an issue once before with a dirty idle air valve, but the problem I had then was that the car wouldn’t start. If you cranked it with your foot on the gas, the engine would turn over, but when you took your foot off the gas, it would die. I was told at the time that the idle air valve is only used when the engine is cold–which made sense, because if you sat with your foot on the gas and revved the engine long enough, then it would run fine. I took it to 3 different mechanics before one of them could identify the problem. What I’m seeing now is that it starts fine, runs rough when it idles, but it seems to be worse when the engine is warm. When it’s stone cold, it’s quieter. But that IS interesting. I hadn’t considered an air problem. I wouldn’t have guessed that there was a close enough link that it would register as a cam sensor issue. DDT Dec 2012 OK, the latest read is now giving P0171 and P0174. They want to replace the computer and O2 sensors. Nevada_545 Dec 2012 Your engine is runnig lean on both banks. If your mass air flow sensor is dirty is isn’t measuring the air that enters your intake manifold properly. Try cleaning the mass air flow sensor first. db4690 Dec 2012 Yeah, and if that doesn’t fix the P0171 and P0174, check these next: Fuel pressure (I’ve seen PLENTY of lean codes because of fuel pressure issues) Check for vacuuum leaks (that includes exhaust leaks in front of the upstream oxygen sensors) I’d be very skeptical about any advice those guys are giving you at this point. Replacing the PCM and the 02 sensors is only worth considering if everything else has been ruled out (granted, there are some situations where a TSB does instruct you to replace the PCM and the 02 sensors, but those aren’t common scenarios). Did those guys say why they want to replace that stuff? - https://community.cartalk.com/t/strange-surging-issue-with-my-88-4runner/78615/3 Old_Toys May 2013 My 99 limited run idles great until the engine reaches the operating temp. (warmed up) It then idles very smooth for approx. 7 secs. and transitions (about 3 secs.) to a rough idle for approx. 7 secs. It continues this pattern for as long as the engine is at normal op temp. The transition period is approx. 3 secs. You could measure time, it’s that sequential. Any ideas are welcomed. It has been doing this for more that a year and very rarely will stall. circuitsmith May 2013 “Any ideas are welcomed” Start a separate thread. - https://community.cartalk.com/t/saturn-97-sl2-5-speed-fast-idle/47228/6 Saturn ‘97 SL2 5 speed - Fast Idle cigroller Apr 2010 Get the codes. I have no idea why you “don’t have much faith” in them. The whole thing really isn’t some kind of scam or something - the computer controls the engine and monitors the major systems. When something is out of spec it stores the error code - they’re called “diagnostic trouble codes” (DTCs) to help you diagnose trouble. When you have them read get the exact code(s) - as in P1234 - https://community.cartalk.com/t/saturn-97-sl2-5-speed-fast-idle/47228/9 bennyandthejets Apr 2010 Actually spraying ether or pressurized propane around suspected vacuum leak areas is a common practice and has been done for years by many mechanics with no negative results. If there is a vacuum leak, it will show up with increased engine speed. --- fixit52 Apr 2010 Sprayed ether around gasket when engine at idle, no increase in RPM as expected if leaking. Is there a better way to check for leaks? JayWB Apr 2010 You sprayed ether around the engine compartment of a running engine looking for vacuum leaks? Well, there’s probably no better way to set your car on fire. --- keith Apr 2010 You need to check when the engine is hot, not cold. Either or propane will increase the idle. If you have a high idle that is a little rough and you spray WD40 over the leak, the idle will actually smooth out and go down to normal. --- mtnbikrec May 2010 propane does work…only just be sure there are no problems with your plug wires…if you have any arcing you can ignite the propane in your face. --- - https://community.cartalk.com/t/maf-sensor-replaced-idle-still-rough/123349/ MAF sensor replaced, idle still rough MY_2_CENTS Aug 2018 Have you checked the air duct between the MAF sensor and the throttle body for cracks or splits? That would also explain the howling noise. It_s-Me Aug 2018 --- Make sure the duct work between the air filter box and the intake manifold is intact, sealed and not cracked, including MAF sensor gasket. checking with propane won’t find that air leak. thegreendrag0n Aug 2018 another idea: check if ECU need to perform “MAF learn” procedure on your engine. This is definitely the case on my Nissan and procedure is very simple to follow (essentially: warm up, stop, disconnect MAF, start the engine and let CEL to get on, re-connect MAF, clean code, let vehicle idle for 15 minutes not touching accelerator). It may be different for another car, but should be possible to find on Chevrolet-specific forums. George_San_Jose1 Aug 2018 ... let us know what the fuel trim measurements are. It sounds to me like it is idling too lean, which should show up in the fuel trims db4690 Nov 2018 You should probably start your own thread That said, can we assume you also have a 2008 Colorado . . . ? Without even laying hands on your car, I’m going to say there’s a pretty strong possibility your engine is misfiring, and may be badly misfiring ALL of the 4- and 5- cylinder engines for this truck were known for having top-end problems, which lead to low compression and severe misfires. This even happens with low-mileage engines Han_So Nov 2018 Oh my god. That sucks. My cheapie obd2 scanner says long term fuel trim is 30. So I bought a smoke machine and did a leak test. No leak. I took it to a mechanic and he did the big obd2 sensor scan and test drove it and checked it all out and said there was absolutely no problem. Still has rough idle. Sounds like I just bought a bad car. Yikes! ykcastrocr_147800 Feb 2019 Hi there, I had the same issue with my truck and stopped when I upgraded to premium fuel, is worth trying… Honda-Blackbird Feb 2019 I believe that I have gotten confused while reading this thread. What exact problem are you trying to solve here? The symptom of “running rough” and MAF do not go hand in hand I’m sorry to say. Also your use of Propane to find leaks thus far is null and void as you arent using it in the proper manner. Propane is used to find vacume leaks that are after the throttle plate… not before it in the air ducting leading to the throttle body. Please describe “running rough” is it an engine miss you are talking about? Is it the idle speed you are discussing? Please elaborate…and never…EVER get repair advice from Auto parts stores, unless you know the person to be a competent automotive guy or a former mechanic. - https://community.cartalk.com/t/1991-chevy-camaro-3-1-v6-rough-idle/163985/2 Mustangman May 2020 --- Also check the vacuum at idle. There are a lot of things that vacuum readings can tell you. https://www.onallcylinders.com/2016/03/31/vac-visual-quick-guide-vacuum-gauge-readings/ --- birdbrainxzx May 2020 fixin the vacuum lines did not fix the problem but we have been clued into something that might be a bit more tragic. the oil smells pretty rich with fuel. texases May 2020 That’s not surprising, old engines running rich have lots of blow by, and I bet you haven’t had it out on the road very often to get the oil up to temperature. ok4450 May 2020 Low compression can cause rich running. Compression should have been checked with the plugs out. Rather than yank the plugs out again (at this point anyway) I would suggest connecting a vacuum gauge to an intake manifold vacuum port to see if there is any abnormality. That’s quick and easy. Depending upon the gauge results then a compression check might be warranted. db4690 May 2020 If I’m not mistaken, the engine should be warmed up, and you’re supposed to make sure the throttle is fully open when doing the compression test I’d do another compression test, warmed up and throttle fully open . . . please post the results If you like, do that wet compression test . . . if the numbers go up dramatically, the bottom end isn’t sealing properly If they don’t rise, the problems are most likely top end . . . perhaps the engine needs a valve job --- birdbrainxzx Mustangman May 2020 It looks like we may have a winner. We replaced the Injectors and regulator today. The old injectors lookedl ike they were mismatched and all of them were missing the lower orings that go into the engine. Got all of that back together and after a bit of priming she started running way better. The exhaust smells more like exhaust and less like bumper boats and hardly any smoke out of her We’re going to run some seafoam through her because I’m assuming there’s a ton of carbon build up from how poor it’s been running. I’ll update if things change. In the meantime, Thank you everyone who contributed. I’ve learned a ton about things to check in these kinds of scenarios. NYBo May 2020 You mentioned the oil smelled of gasoline. Have you changed it? If not, do so before running the engine. - https://community.cartalk.com/t/alfa-75-3-0-v6-bogging-on-acceleration-slow-to-start/109395 Alfa 75 3.0 V6 Bogging on Acceleration & Slow to Start jackocooper Nov 2017 My 1988 Alfa 75 3.0 V6 --- ... I had an issue with the fuel injector o-rings leaking air causing a misfire. I’ve since replaced these and it’s now running on all 6 cylinders. (before I replaced the o-rings, the bogging issue was significantly worse). --- - https://community.cartalk.com/t/alfa-75-3-0-v6-bogging-on-acceleration-slow-to-start/109395/25 Alfa 75 3.0 V6 Bogging on Acceleration & Slow to Start alfaromeo --- When I read your comment “The car runs well for a minute or so, then will run poorly for a min or so. When running poorly, there is a lack in power, fluctuating idle, splutter when reving (sometimes with backfire), occasional stalling.” my first thought is a problem with the ignition system that generates the spark. That’s often heat sensitive and intermittent. On my Rabbit it was just a points and single coil system. The only problem I ever had was a cracked coil that made it stall if I ran over a puddle of water. The crack was on the underside and so tiny it was nearly impossible to see. For the Rabbit, it was a big coil on the firewall, not the small coils more common now that are located inside the distributor. If you have a big coil like that, remove it, clean it up, and inspect it on the bench under good lighting & using a magnifying glass for really tiny cracks. If you have a coil and ignition module inside the distributor, which senses the distributor shaft turning to synch up with the crankshaft, that could be the problem. I should add that o’scope testing of the ignition system is very helpful to diagnose an ignition system problem. That’s what I’d do first if I had the same symptoms with one of my cars. If you lack the equipment or knowledge how to do it, at some point your best bet may be to have to ask a shop do an o’scope analysis. --- jackocooper Jan 2018 SOLVED! Looks like I’ve finally found the problem. The intank mesh fuel filter, although looked spotless, wasn’t letting much fuel through. So when the car was sat for a while, the pipe between the tank and the pump slowly filled with fuel so the car would run for 10 minutes, however not enough fuel was coming out of the tank, causing the pump to whine and the car to bog under acceleration. I took out this old intank filter and the fuel flowed like it should. I’ve installed a new filter before the pump and the car runs perfectly. Thanks for all your help over the past few months! Onto the MOT now. https://community.cartalk.com/t/2001-sonata-p0171-surging-strong-exhaust-smell/108123/4 2001 Sonata - P0171, Surging, strong exhaust smell the_same_mountainbike Sep 2017 --- Black soot comes from incomplete combustion of the fuel (or rich metering, but I don’t think that’s the problem in this case). Pressure to the dipstick tube comes from the crankcase. A clogged Positive Crankcase Pressure (PCV) valve can cause it to build to excess, but in this 16 year old engine I suspect it’s cylinder wear. All engines have some level of combustion that blows past the rings and pressurizes the crankcase (blowby). The weaker the seal is between the rings and the cylinders is the more the crankcase becomes pressurized from the combustion gasses. In severe wear cases, it can blow the dipstick out. --- George_San_Jose1 Sep 2017 Assuming routine maintenance is up to date, engine and valve timing check out ok at idle, then blocked exhaust, EGR sticking open, or PCV system clogged up or hoses hooked up wrong is where I’d focus w/this problem. Start w/the EGR, that’s pretty easy to test if it is sticking open or not. It shouldn’t be open much if all at idle, so figure out a way to control it to open as a test, the engine should stall out or run much rougher at idle with the EGR open. Does it? George_San_Jose1 Sep 2017 --- The surging you are experiencing could be caused by too much fuel being injected, a stuck-on injector maybe. With that problem, at idle it would run rich and not idle well, and a lot of black smoke out the exhaust comes with being too rich, and when you step on the gas more air is allowed in which, when mixed with the extra gas, will cause an engine surge. The problem w/this theory is that you are getting a lean code, not a rich code. A lean code would usually be caused by an intake leak or an exhaust leak. --- George_San_Jose1 Oct 2017 Suggest to replace the PCV valve with a new one. Inexpensive part. And if it is sticking you’ll have more problems than just black smoke out the exhaust pipe. Damaged crankshaft seals eventually, something you definitely don’t want. The dipstick popping out can be a symptom of a problematic PCV system. As I recall you have really good compression numbers, so it seems unlikely the crankcase pressure could be caused by leaky piston-compression rings. George_San_Jose1 Sep 2015 Modern engines – electronic fuel injected, like yours --have to be air tight all the way from the throttle body to the exhaust pipe. Otherwise they won’t work correctly. So before you fret over all the possibilities, get that exhaust leak fixed first. --- If the wandering rpm problem continues, my first guess is that the idle adjustment screw is out of whack. Cars of that era tended to have this adjustment, while newer cars it has been eliminated. My early 90’s Corolla has it for example. Sometimes a diy’er or mechanic will adjust the idle adjustment screw in an attempt to solve some problem or another, when that’s not what’s causing the problem. The result is a difficult to diagnose wandering idle rpm. That’s why that adjustment was later eliminated . What happens, the computer is confused why the car is idling the way it is , so it tries to change the idle to get it back in spec, like by advancing the timing or adjusting the mixture, which throws something else out of whack. And round and round it goes. The computer assumes the idle adjustment screw is set within narrow limits, and if it is set outside those limits the computer won’t be able to maintain a steady idle. --- - https://community.cartalk.com/t/can-compression-test-diagnose-tiny-leaks/87132/4 Can Compression Test Diagnose Tiny Leaks? Tester Sep 2014 A leak-down test is where compressed air is introduced into a cylinder with the piston at top-dead-center. Here’s the leak-down-tester. http://www.harborfreight.com/cylinder-leak-down-tester-94190.html 7 At top-dead-center, both the intake and exhaust valves are closed. When the compressed air is introduced, it can be determined if there’s a problem with that cylinder. If air is heard coming out the exhaust pipe there’s an exhaust valve problem. If air is heard coming out the throttle body/carburator there’s an intake valve problem. If air is heard out of the oil dip stick tube there’s a ring problem. And if bubbles form in the coolant in the radiator there’s a head gasket problem. Tester George_San_Jose1 Sep 2014 Rough idles and misfires on cold starts could be caused by an assortment of things. I suggest before you start making up a testing plan, start with the actual symptom(s) and what others here think the most likely causes could be. Rough idle problems are often caused by faulty or dirty IAC, dirty throttle bodies, dirty fuel injectors, or air leaks. Diagnosing misfires occurring on specific cylinders often involves a process where you move things around and note whether the problem tracks what you moved. General misfires where it occurs seemingly at random over all he cylinders is often a sensor problem. If you want to eliminate the head gasket as the source of the problem, my advice is to take the car to a good inde mechanic and ask them to do the necessary tests. I think you’d get better results that way and spend less time and money in the process. I’m all in favor of DIYers, but sometimes it is better to trust the job to someone who has done it many times before. Especially when the job is a narrowly defined task like: Does this engine have a head gasket leak.? db4690 Sep 2014 Here’s a wild thought . . . I’m wondering if you may have low compression when cold, due to the valves This would be a valve lash issue, though. With the engine cold, the valve lash is insufficient, and you have low compression. Which leads to hard starting and a rough idle for a time. Then things warm up, the valves seat better, compression goes up. At which point, you can shut it off, and restart a few minutes later with no problem I’m going to guess this engine has hydraulic lifters, but that doesn’t mean they’re functioning correctly As I said, this was just a wild thought - https://community.cartalk.com/t/engine-runs-awful/57159 Engine runs awful bigreddon Nov 2010 what could be wrong with it? timing belt ok timing ok compression ok spark ok fuel pressure ok cylinder 6 spits sir out of intake when doing compression test, but has 150 lbs compression and no cylinder leakage with cylinder leak tester mark9207 Nov 2010 You may be entirely on the wrong track to diagnosing this problem. Many issues with the way an engine runs are much more likely to be electronic or sensor related than mechanical in nature. Some mechanical problems that can influence sensors should also be explored, such as vacuum leaks. Have you checked for trouble codes or had the vehicle scanned to watch the behavior of sensors and other components? Lastly, could you be a little more descriptive about what the problem is other than that the engine “runs awful”? bigreddon Nov 2010 It stumbles and backfires and idles rough. it was running really really well and as it was warming up, it suddenly started to run terrible, as if the “run terrible” switch had been turned on. i have a scanner, and many many codes were found. i wrote them all down, cleared them, and got one code for engine misfire cylinder 6. then additional codes started to appear. i summized the misfire was causing other error codes. i checked spark and vacuum and the spark was hot and the vacuum was at 18 in merc. since this last email i have found the problem… jayjayp47 Nov 2010 …and the problem is/was?? It is useful and helpful to all to know the outcomes. bigreddon Nov 2010 the problem was a broken exhaust cam. the air spitting out was actually the exhaust not being able to exit through the exhaust port, and due to the slight overlap of intake and exhaust valve timing, the exhaust would actually exit the intake just as the intake valve opened. the higher compression on that cylinder was a result of a “double compression stroke”, since instead of exhausting, it actually compressed the exhaust. the cam was broken right in the center of the adjascent cylinder, and that cylinder only had one exhaust valve functioning. picked up a used cam today for 18 dollars and will keep ya posted… - https://community.cartalk.com/t/2002-hyundai-elantra-idling-rough/118488/11 2002 Hyundai Elantra idling rough TommyColbert Jun 2018 Dear Car Talk --- At that time the service engine light came on and it is idling rough in drive and runs about 3500 rpms in park .A friend did an analysis and it showed a throttle position sensor problem.We replaced the sensor but that didn’t correct the problem. A second analysis didn’t show the sensor problem but showed misfires on two cylinders . My friend thinks the problem is a clogged fuel system and suggest that I drive the car for a while and use a fuel cleaning additive. Does this sound logical to you. I would hate to drive the car and ruin the engine. Tommy George_San_Jose1 Jun 2018 If driving the car seems to help, good chance there’s some gunk in the fuel system or spark plug tips. Once the engine warms up, try to run the car at freeway speeds for 3-4 miles a couple of times a week. - https://community.cartalk.com/t/2000-silverado-2500-6-0-random-lack-of-power/90575/7 2000 silverado 2500 6.0 random lack of power db4690 Jul 2015 --- Of the 2 things I mentioned, in my experience, the intake gaskets are FAR more likely to cause rough idling But an exhaust leak can most definitely cause fuel rims out of whack. Seen it plenty of times --- - https://community.cartalk.com/t/73-ford-truck-idling-poorly/92892 73 Ford truck idling poorly George_San_Jose1 Mar 2016 --- Then about three weeks ago it started to idle rough, and over the next week or two started to increasingly sputter and cough at idle, stalling occasionally. Warm or cold engine, no matter. Although it seems a little more noticeable when the engine is cold. The symptom, whatever the cause, is progressively getting worse. When I feel (with the back of my hand) and listen to the exhaust stream at idle, there’s a definite sign of engine missing. It’s not the normal rhythmic “put-put-put”, but more like put-put — sigh – put-put-put – sigh … well you get the idea. Something’s definitely not right. It seems to me like the air/fuel mixture is way too lean when this is happening. The biggest clue I’ve got is that this problem goes completely away with the throttle even slightly above idle. Idle rpm is about 750, and if the rpm is over 1000 by pressing on the gas pedal, much improved. And acceleration performance from 15 mph to 60 mph remains perfect, a lot of ummmph, no missing at all. Under 15 mph, very noticeable rough running and missing. Here’s what I’ve done Plugged all the vacuum sources, both intake manifold and carb. So no vacuum leaks from any of those are possible. No difference. Filled the tank with fresh gasoline, thinking it might have been a case of bad gas. No difference. Idle timing is spot on Timing advances with rpm like it should so distributor centrifugal weights are working. Dwell is spot on Everything inside distributor looks like new, no signs of carbon tracking, points in good shape Idle rpm is correct on average, but unstable. Surging is noticed if I increase the idle rpm beyond spec. Driving at 20 mph, no missing, but surging causing the speed to increase and decrease slightly remains. No change with or without air cleaner installed. I did discover a couple of problems with some vacuum operated gadgets, the air cleaner vacuum motor and a temperature controlled vacuum switch, but those are now completely disconnected and no change. Next up on my plan Remove the vacuum operated gadget on the carb that controls the choke, see if the diaphragm has a leak in it. That’s the only obvious place a vacuum leak could be happening now. Replace the fuel filter. Replace points/condenser, spark plugs. This hasn’t been done in a number of years, but less than 30 K miles ago. Remove the carb and take it apart, look for something plugged up, rebuild if necessary. Beyond all that, any ideas? Is the clue where the problem goes completely away just off-idle important ? George_San_Jose1 Mar 2016 @Tester … Ethanol in the gasoline? Not that I know of. I’ve used the same gas station for the past three years for gassing up the truck and never had a problem before. It is possible they changed the formula I guess. I looked through the maintenance and repair file to see if I’ve ever had this kind of poor idle that comes on quickly before. It’s happened on three occasions. 1. Split vacuum hose t-connector 2. Split diaphragm in the air cleaner vacuum motor 3. That choke gadget that sits on top of the carb had to be replaced. It’s that triangle shaped thing on the upper left of this photo. http://i.ebayimg.com/00/s/MzAwWDQwMA==/z/r0MAAMXQVT9SsSQ3/$_3.JPG?set_id=2 24 I’ve eliminated 1 & 2, but 3 is still an open issue. the_same_mountainbike Mar 2016 Question to Rod, are these gaskets subject to degradation due to ethanol? If so, perhaps the carb needs to be totally rebuilt using a kit with elastomerics not sensitive to same. Just a thought. I know little about this vehicle. To the OP: rebuilding the carb (last item on your list) sounds like an excellent plan. The float in old carbs is usually either made of thin stamped metal or a molded material that over time will begin to deteriorate and leak (the stamped metal ones) or absorb gas. Either condition can cause the float to not float so well anymore. If that happens, it no longer properly operates the needle valve that regulates the flow of gas into the bowl, causing metering problems… causing erratic operation. These are just general thoughts. I’ve rebuilt carbs before many years ago, but never one from this engine, nor do I have any hands-on experience with this engine. --- George_San_Jose1 Mar 2016 @edb1961 … yes, it has both vacuum advance and vacuum retard. Both work correctly. Both are currently disconnected from their vacuum source so they aren’t doing anything at the moment. Idle timing remains spot on. --- Renegade Mar 2016 I think Testert is right obout the ethanol. I have an 82 dodge pickup with a 318 My mechanic told me to try non ethanol to see what happens. It made a big difference now runs like it should George_San_Jose1 Mar 2016 Well, they are switching to the summer formula right about now. Maybe something to that. But I’ve never had any problems before with either the winter or summer formulas. Tester Mar 2016 @GeorgeSanJose Answer a simple question! Are you using ethanol gas? Yes or No? Tester George_San_Jose1 Mar 2016 Not sure. I’m not intending to. There’s no label on the gas pump which says what is in the gasoline. ok4450 Mar 2016 There are a number of things that can cause a rough idle. It can be something as simple as a vacuum leak or carb problem or more major such as a compression issue or valve spring problem. I tend to dismiss the major stuff at this point. What would I do? My first step would be to connect a vacuum gauge. That’s cheap, easy, and can tell you a lot about what’s going on as to whether there’s a vacuum leak, ignition miss, etc, etc. Offhand, I might suspect some moisture in the float bowl of the carb or a piece of grit in an air bleed or emulsion tube. You could try removing the mixture screws from the carb and liberally spray some aerosol carb cleaner in to the holes. Ideally, this should be followed up with compressed air. Just a short tale about air bleeds. Back in the late 80 or early 90s I overhauled an EEC controlled carburetor on a Subaru for a guy. The air filter was absolutely filthy and he flat refused to pay for a new one. He said that he would pick one up and do it himself. I then told him no warranty on the work. Two weeks later this car came back to me on a wrecker after dying suddenly. Slightly pissed off, I looked and sure enough, that old air filter was still in there.I then took the air gun and forced air through the primary air bleeds. The car started right up and ran fine. Apparently a piece of sand or grit had dislodged from the air filter and it just happened to hit the air bleed while the engine was at idle. If it had happened at elevated RPMs the junk would have gone down the primary bore and never been a problem. Nevada_545 Mar 2016 First, be sure all scheduled maintenance is up to date. (That’s an old favorite, right George?) Ethanol gasoline or E10 is nearly unavoidable in the southwest. In the 1990s I drove a 1973 Grand Torino, I had to replace the accelerator pump every 18 months because the ethanol would harden the pump seal. On your truck I suspect the power valve diaphragm has ruptured and unmetered fuel is dripping into the manifold. Mustangman Mar 2016 I think @Rod Knox and @ok4450 have the right idea. There is a vacuum leak in some gasket somewhere. Whether it is ethanol induced or not, it needs to be identified. As others have pointed out, ethanol needs to be dealt with. Fuel pumps, lines, carb gaskets ect, are all affected and will likely eventually succumb to ethanol. Might be a good time to swap those points out for a modern electronic ignition, too. pertronix.com/prod/ig/ignitor/default.aspx Rod-Knox Mar 2016 The EGR spacer and gaskets were a problem before ethanol was mandated. And finding non-ethanol gasoline can be a pain and when found it is 50c higher than the ‘10% ethanol stuff.’ insightful Mar 2016 Step one: Pull the plugs for a look-see. Rod-Knox Apr 2016 In trying to recollect dealing with driveability problems such as the OP’s back in the GOOD OLE DAYS I recall tipping the choke to significantly close it and listening for an improvement in the idle and also lifting the coil wire up slightly from the distributor cap. And to think how outrageous the electronic ignitions of the early 70s looked to mechanics at the time seems silly compared to today’s computerized COP ignitions. Barkydog Apr 2016 Does it seem like it is running rich or lean? If running lean carb cleaning, rich replace needle and seat in the float bowl, a cheap easy thing to do. UncleTurbo Apr 2016 I’ll take the stance that the ethanol fuel has crapped out the carb. I think the carb will need to come off for a rebuild or you can buy a new carb. Most rebuilds will use rubber parts that will handle the ethanol fuel in the future if we stay with 10% ethanol or lower. Unfortunately that doesn’t update the rest of the fuel system, fuel pump, rubber fuel lines, etc. I’d highly recommend treating all the gas with a marine grade ethanol treatment. sgtrock21 Apr 2016 Nevada_545: The “choke gadget” on top of the carb also looks like an accelerator pump to me. George_San_Jose1 Apr 2016 @sgtrock21 … no, that triangle gadget on top of the carb – as shown in the photo-link I posted above – is not the accelerator pump. The accelerator pump is on the front of the carb. I’ve had to change the diaphragm in the accel pump a number of times over the years. But it’s likely not the current problem. When the accel pump diaphragm splits it leaks gasoline, which is easy to see. And it isn’t leaking. That triangle gadget, not entirely sure everything what it does but part of its function is involved in the choke system. It seems to be what holds the choke plate slightly open once the engine starts. I did have to replace that gadget before due to a split diaphragm, but the current one seems to be functioning correctly now. At least it is cocking the choke plate ajar one the engine starts as expected. Easy enough to remove and eyeball the diaphragm though, and know for sure. @ok4450 … Now I think about it, you are likely correct about partially clogged idle bleed screws. I’m placing that theory as of now as the highest priority. The symptom is very consistent, running horribly at idle, then runs fine with the throttle plate even slightly off idle. I did a little research on how carbs work the other day, both Rochester and Holley designs, and what the books said was the main idle port is below the throttle plate at full idle, so that’s the main path for gasoline to squirt into and run the engine with the throttle plate closed to its nominal idle position. But when the throttle plate is even slightly cracked open, that allows a secondary idle port just above the throttle plate nominal position to supply fuel. That’s the off-idle port. And by the engine performance I’m experiencing, that one must be open and working fine. The other thing consistent with your idea is I in fact did let the air cleaner go a little too long. It was noticeably dirty. I’ve installed a new one, but I’ll have to remove those idle air mixture screws and clean those holes out by squirting some carb cleaner in there. @Nevada_545 and others, thanks, good comments. With a 40+ year old truck, it could be anything. If none of the quick fixes work, I’ll measure compression, fuel pressure, rebuild the carb, replace the fuel filter, spark plugs, points, condenser, dist cap, and wires and report back. the_same_mountainbike Apr 2016 Manual chokes go back much farther than the '70s. By 1970 every vehicle I can remember had an automatic choke. Heck, my '64 Fairlane had an automatic choke. --- George_San_Jose1 Apr 2016 @texases … The existing HV wires have seen 6 years, maybe 15,000 miles. I gave them the twist-and-look treatment and see no signs of insulation deterioration. They’re of the silicone rubber type, which seem to hold up pretty good. As suggested above, I idled the engine in the dark and see no signs of sparks jumping around under the hood. That and the fact that the symptom is very dependent on throttle position makes me think the most likely explanation is a fuel/air mixture problem at idle. George_San_Jose1 Apr 2016 Update. Cleaned out idle-screw adjustment ports with carb spray with carb installed. Replaced fuel filter. Took a sample of the gas in the tank by re-routing the fuel line from the carb intake to a container and running the starter motor 15 seconds. No signs of fuel contamination or separation. Checked capacitance of ignition condenser, measured 0.22 uF , same as a new replacement, so left it in place. Overall, definite improvement at idle rpm, but some idle missing and idle rpm surging still present. Off idle performance remains the same, like new. Next up, carb rebuild and egr replacement. BillRussell Apr 2016 Measuring a capacitor’s value in µF tells you nothing about the cap’s performance at high voltages. It’s cheap enough, replace it. George_San_Jose1 Apr 2016 Does that cap experience high voltages? How high? BillRussell Apr 2016 The distributor and the points see thousands of volts. The capacitor is on the primary of the coil and sees several hundred volts. (confusion between distributor CAP and CAPacitor) George_San_Jose1 Apr 2016 Interesting. I thought the condenser, being in the primary circuit, only experienced voltages in the 12 volt-15 volt range. You are correct, my capacitance measurement test was only done at low voltage, so the condenser remains suspect. As a counterpoint, the engine performs normally at rpms off idle, which seems inconsistent with a condenser failure. BTW, I did buy a replacement already, which cost – sort of hard to believe for a capacitor – $14. BillRussell Apr 2016 The capacitor, with the primary coil inductance, form a resonant circuit, which, when the switch (points) open, causes an inductive kick to hundreds of volts. The transformer ups that to thousands of volts for the spark. George_San_Jose1 Apr 2016 What you say makes complete sense @BillRussell . Just curious, what’s the expected symptom if the condenser isn’t working? I’ve always heard it shows up as burned and pitted points, the condensor’s job being to limit the voltage at the points to prevent sparks jumping there between the two point contacts. ok4450 Apr 2016 On the few condenser failures I’ve seen the symptom was similar to a carbed engine that is flooding. Bucking and jerking, some black smoke, etc. The engine would die now and then, sit for a while until things cooled off a bit, and then may run again for an unspecified amount of time until the symptom resurfaces. George_San_Jose1 May 2016 This AM I finally had some dedicated time to work on this, and can report the problem is now resolved. 70’s Ford truck 302 V8 engine idling and running smoothly again. The major problems turned out to be: The gasket between the EGR spacer plate had a hole burned clean through it, all the way out to the edge, creating a vacuum leak directly into the intake manifold. I replaced that gasket, cleaned the mating surfaces (which was a pretty big job), cleaned out the EGR holes in the spacer from carbon deposits, and replaced the EGR valve w/a new one. Some of the carb passages were clogged. I think the main problem was a clog somewhere between the jets and where the idle ports emerge higher up, near the venturi booster ass’y. So I bought a carb rebuild kit, which included a new float valve ass’y, power valve, accel pump, and various gaskets and clips, all of which I installed. The technique I’ve used in the past for rebuilding the carb by removing the carb from the vehicle, then removing the air horn, the jets, the float ass’y, the accel pump, the venture booster, and the power valve and spraying all the passages with carb cleaner spray wasn’t effective. I tried that 2 times, worked for a while, but didn’t take. On the third time I decided to bite the bullet & remove the entire choke ass’y and various other gadgets, then thoroughly clean the exterior of the carb of all the gunk. That part is time consuming for a diy’er without a parts washer, that’s the reason I wanted to avoid that task, but it was necessary this time. Next I soaked the entire carb body in a bucket of Berryman’s carb soaking solution for 20 minutes. Then I soaked the carb in a water bath to clean off the Berryman’s, then sprayed the carb & passages with carb cleaner, then used some 30 AWG wire to explore and verify the passages remained unblocked. One thing good about this wire task, I think I better understand how this carb works & how it was manufactured. Finally I sprayed all the passages with compressed air in the reverse flow direction using an air gun and compressor set at 35 psi. Contributing factors were fuel and engine air filters that were past their prime, which I replaced. I added a second fuel filter in line with the oem filter, with a clear housing, so can visually check for any debris in the fuel lines. So far I don’t see anything accumulating there. While everything was removed, decided that was a good time to replace the spark plugs. Access to number 8 can be beastly, but with everything removed and the pathway clear, and a little tinker-toy engineering of the ratchet configuration, number 8 popped out in a snap. Visual inspection of the old plugs showed them to all be in good condition, the gap pretty much unchanged, but there is a slight indication of a problem on number 6, the insulating ceramic adjacent to the gap was gunked up, which I think might be caused by a dodgy spark plug wire causing an occasional misfire. I think that b/c that spark plug wire zapped me a couple of time when I touched it near the boot, and none of the others do. Upon reassembly and reinstallation of the carb on the engine, it started right up and idled smoothly again. Many thanks @“Rod Knox” who suggested the soak idea, and investigate the EGR spacer, and what that triangle gadget is (choke pull-down, which tested ok), and to finish off the job with a compressed air spray through all the passages; to @TwinTurbo for the suggestion to secure the correct tool to remove the jets; to @“Honda Blackbird” for suggesting heat to remove the jets (I used cold rather than heat, but same idea); to @wentwest for suggesting thin wire to check and clean the passages; to @Nevada_545 for suggesting to investigate the power valve (turned out to not be the problem); to @“the same mountainbike” for suggesting to make sure the float floats, the fuel pump pumps, and dizzy dizzies (none were the problem); to @Tester for suggesting it might be caused by ethanol in the fuel (probably not the problem, but keeping this in mind if future fuel system problems develop); to @insightful and @pleasedodgevan2 for suggesting to check the spark plugs and wires and ignition system; and @ok4450 for suggesting to check the intake manifold vacuum (seems ok, measures 18-20 at idle now). For reference purposes for those interested, the following thread was a spin-off from this one. http://community.cartalk.com/discussion/2307884/stuck-carburetor-jet/p1 Rod-Knox May 2016 Congratulations @George. Funny how things fall right into place for those who are willing to go the extra mile and do things correctly. Lazy people call it luck. - https://community.cartalk.com/t/retorquing-bolts-after-gasket-replacement/193587 Retorquing bolts after gasket replacement enargins Oct 2023 So, I just had the valve cover gaskets and the exhaust manifold gaskets in my 2003 Dodge Caravan SE (3.3L flex fuel engine) replaced. After a bit the car started experiencing a rough idle, where the car would vibrate when idling. When first started, the vibration would be faint, but once the engine was warmed up, the vibration at idle would be very pronounced. George_San_Jose1 Oct 2023 The vibration may be an engine misfire symptom. Usually this would turn on the CEL, but sometimes it takes several drive cycles before the warning light on the dashboard turns on. Ask your shop to check the computer memory for pending diagnostic codes. Not something to be ignored or deferred b/c engine misfires can damage the catalytic converter. As far as whether replacing the gaskets is the cause of the vibration, as long as there’s now loud banging exhaust sounds, seems pretty unlikely to be a gasket installation or re-torquing problem. But it could be that something else was left disconnected or not properly buttoned up afterward. The shop probably has to remove a bunch of stuff that’s in the way as part of the gasket job. I think it is a good idea to re-torque the exhaust manifold gaskets every once in a while, but 100 miles seems too soon. Maybe every 6 months to a year, 5k/10k miles. bing Oct 2023 The first thing I would check for is an air leak, hose that came off or old and not a good seal. At least that was the problem with the 61 lark 50 years ago. Ran terrible, vibrated, etc. about a 5 minute job including opening the hood and trimming the end of the hose by a smart aleck college kid. enargins Oct 2023 So, I spoke with the service manager. He said they didn’t have a chance to look at it in detail today. Said they’re going to put it up on the rack tomorrow and take a closer look at it. --- I asked why I didn’t feel that before. He said it’s possible that when they were messing with the exhaust manifold that they knocked it, and the rubber got pushed out of place. He said that’s the only thing that makes sense to him. Also, I asked about possible misfire codes, and he said they checked the live data while it was running, and there were no misfires. I asked him about the possibility of it being an air hose leak, and he said they’d check for that tomorrow. So that’s the latest. Nevada_545 Oct 2023 enargins: I asked about possible misfire codes, The check engine light will flash while the engine is a misfiring, then remain on for the duration of that ignition cycle, you would have noticed that while driving a night. enargins Oct 2023 Just spoke with the service manager. Said they checked the fuel trim and it was spot on, between 1.8 and 2.5, so he didn’t think there was a vacuum hose leak. Said they checked the engine mounts, and only the front one, next to the exhaust manifold, seemed bad. So they went ahead and replaced it. Said they’re taking it for a test drive now, but so far everything looks good. enargins Oct 2023 UPDATE So, I guess the manager spoke too soon. The vibration is a little better, but not much. The small vibration that was there when it was in Park is completely gone, and back to how it was before. But the large vibrations when it’s in Drive are still there, though a little better. Previously, the Drive vibrations were so bad you’d feel them in your body when your hands were on the steering wheel. Now that’s no longer the case, but the steering wheel is still vibrating very bad. On a scale of 1 to 10, if the previous vibrations were a 10, then they are now about a 7. The service manager said he didn’t know what else it could be. Said the side mounts both looked good. Said he wasn’t sure about the rear mount, though. He said they’ll bring it back up on the lift and double-check the mounts, especially the rear one. He said the rear one is really the only other one that could be the issue. So he’s going to let me know what happens once they recheck the mounts. Other than that, he said he doesn’t know what it could be. George_San_Jose1 Oct 2023 An engine vibration that’s neither a misfire nor a problematic mount may take some time to find. Suggest to briefly post everything engine-related that has changed, including how many days ago the change(s) occurred, since the last time there was no similar vibration. old_mopar_guy Oct 2023 Please George, no! We’re already at post #62. George_San_Jose1 Oct 2023 That’s why I’m asking for a summary, … lol … can you think of any reason for OP’s engine vibration suddenly developing other than a misfire? enargins Oct 2023 UPDATE So, they checked the rear mount, and it had some cracks in it, so they replaced it. Said the side mounts both looked fine. So front and rear mounts are now new. So I picked up the car, as there’s not much else they could do. So, basically, right now it has strong vibrations at idle when in Drive or Reverse (but not Park). And the vibrations continue (though much less) when driving slowly. But once you get over a few miles per hour the drive is smooth. No vibrations. That would SEEM to be an air/fuel issue (based on my very limited understanding of car mechanics). But he said they checked the air/fuel ratio when the car was idling, and it was correct (numbers noted in previous post). So I don’t know what else it could be. I’m just glad it doesn’t do it while I’m driving. 9/16 - 106,659 miles: No vibrations. Car had emission leak from fuel tank which was throwing a code, and catalytic converter was throwing a code. Shop ordered new fuel tank from salvage yard, but it also had a leak, so they just repaired the leak in the tank’s rollover valve. Fuel pump had been making noise for a while, so they replaced fuel pump when the fuel tank repair was done. Catalytic converter was replaced. Oxygen sensors broke when they were replacing cat, so they replaced the oxygen sensors. After replacing cat, fuel gauge stopped working properly. Checked all outputs from the fuel pump, everything was fine. Checked electrical inputs, etc., all fine. So they replaced cluster with a new used cluster. 10/23 - 106,760 miles: New catalytic converter made noise when accelerating. Checked everything, looked for leaks, replaced gaskets. Nothing fixed the problem. They determined that the problem was the exhaust manifold gasket, as they found a small leak from it. Replaced exhaust manifold gasket. Valve cover gaskets had been leaking for some time, so replaced those as well. Replacing exhaust manifold gasket didn’t stop the noise, so they replaced the cat with another catalytic converter, and that solved the problem. Vibrations were first noticed after picking up the car after this work was done. Thanks! old_mopar_guy Oct 2023 Nope. I wouldnt hazard a guess without ALL the appropriate data. Frankly, with the age of this van, it’s simply not worth it to track something like this down. George_San_Jose1 Oct 2023 Confusing. Suggest to repost the vehicle repair history, this time starting from the most recent date there were no vibrations. There’s no need to go further back than that. Brief post, please. Only what was done, not why, or what else they checked. YoshiMoshi3 Oct 2023 Sometimes with older cars with lots of miles, they just make noises. Well there is always a reason, it doesn’t “just happen for no reason”, but if nothing appears to be wrong, not much you can do. You will drive yourself nuts, and spend money on parts that don’t really need to be replaced. Not worth spending the money or time, especially on an older car that his high mileage that may not be worth much. You will spend more money on repairs than the car is worth. If no major side effects exist from the vibration with no apparent cause, might just want to ignore it. enargins Oct 2023 keith: Does the vehicle have to be moving to feel the vibrations? No, actually the opposite. The vibrations are only felt when it’s standing still and idling. In Park you can feel them a little. But in Drive or Reverse (with brake pressed) they’re very strong. --- YoshiMoshi3 Oct 2023 --- But yes, on a car this old, I assume high mileage and probably not worth much (I drive a car that you can describe as such myself), things with no apparent cause or negative impacts, might be best to “just ignore” until it’s more obvious what the problem is. --- eddo Oct 2023 @enargins How many miles/ how much driving time have been done since you picked this van up with the vibration? I ask because it is possible that since repairs were done and DTC’s were seemingly cleared, that the ECM has not yet completed a drive cycle and thus not yet relearned all of the data it needs to know where baselines are. Essentially, the engine is running on defaults until it relearns everything, then your idle may smooth out. If it hasn’t been long (in terms of miles or drive time- NOT calendar time,) I suggest to drive for a week or so and see if that helps anything. Tester Oct 2023Clearing a diagnostic code shouldn’t cause the engine to run rough at all. Could you imagine every time any code was cleared that the engine vibrated badly until the readiness monitors completed? There’s something else wrong with this vehicle. Tester eddo Oct 2023 I don’t necessarily disagree with you- but I’ve seen it happen on older vehicles. Tester Oct 2023 I can’t tell you how many diagnostic codes I’ve cleared over the years. And I’ve never had an engine operate as bad and for as long as you describe doing so. Tester keith Oct 2023 OK, something we haven’t looked at yet. The valve cover gaskets were replaced. On most V-6 engines with a 60 degree V, the intake manifold has to be removed if one piece, or the top half (plenum) has to be removed if two piece. This can result in a vacuum leak that results in uneven vacuum between the intake ports, especially if the whole manifold has to be replaced. I don’t see anything about the intake manifold gasket or the plenum gasket being replaced. Often the plenum gasket is a series of O-rings that supposedly can be reused, but if one is leaking, it will cause an uneven idle, especially in gear where the idle speed is at its lowest. One indicator of this is that the idle speed in neutral will be 200 rpm or more above the normal idle speed. That usually turns out to be about 950 rpm or higher when at operating temperature. If this is the case, your shop did a lot of unnecessary work, except if you did have an exhaust leak and it appears that you did, that has to be fixed. keith Oct 2023 enargins: Re. vacuum leak, that was one of the things I asked about, and they said that the air/fuel mixture was spot on, and if there was a vacuum leak, it would be off. The air/fuel mix for the whole engine would be spot on, but the air/fuel mix can still vary from cylinder to cylinder. Using the OBDII data is not a test for this. A smoke test for this is also somewhat unreliable because access to the full circumference of the port is limited. The usual test is to spray a light oil (WD-40) around the circumference of each port and watch for a change in the idle speed or smoothness. When you find the leaking port, the idle speed will drop and smooth out. But any change in the idle indicates that you found the leak. The problem with doing this on a V-6 is access to the full circumference of each port. If you have a propane torch, with the engine running, use the torch, unlit, to spray raw propane around the intake manifold ports and if the idle speed jumps, you have a leak. Jerome-Silverman Nov 2023 With one cylinder misfiring, naturally, the vibration amplitude would be worse at low engine speeds and at a rate proportional to the engine speed. Also acceleration would be slower and high speed might not be possible. . The cylinders fire one at a time, in regular sequence. The pulsations of energy are absorbed and smoothed out somewhat by the mass of the flywheel, rotating parts, drive train, and the rest of the vehicle, as engaged at any particular time. keith Nov 2023 It is normal for a fouled plug to only cause vibrations at low speed. Any regular misfire will be felt only at idle or low speed because as the engine RPM build up, the inertia of the rotating parts will smooth out the vibrations. But if you have a misfire, you will also have a check engine light with a code of P03xx. The xx is the cylinder number, I.e P0301 would be the number one cylinder. A P0300 means a random cylinder misfire. You can have a vibration but not show a misfire because all the plugs are firing. You can find the errant cylinder by pulling a plug wire, one at a time to find the cylinder that is least affected but with today’s modern epoxy coils, that can damage them. You could however just disconnect the firing signal from the computer by disconnecting the plug from the computer at the coil end. - https://community.cartalk.com/t/1989-chrysler-fifth-avenue-still-idling-rough-stalling-after-carburetor-work/190913/11 1989 Chrysler Fifth Avenue still idling rough/stalling after carburetor work? George_San_Jose1 Jun 2023 No experience with your car, but I recently had similar problem with older Ford carbureted truck. Poor idle, misfiring at idle when engine warm, but idled ok cold, and ran well at higher rpms, no misfires when rapidly accelerating or going fast. Long story short, after some experiments with ignition system that had no effect, I removed the carb and cleaned its idle pathways. Reinstalled carb, problem solved. Noticed some grit at bottom of carb fuel bowl, so replaced fuel filter as part of job. As mentioned above, your carb is considerably more complicated than my truck’s. They were doing everything possible to meet fed clean air standards using a carb, yet not be forced to switch to fuel injection. Were I in your situation though I’d replace everything that is clearly near the end of its life, clean the carb’s idle pathways, replace the air and fuel filters, eliminate all vacuum system leaks, and go from there. - https://community.cartalk.com/t/techron-too-much/50135/15 Techron - too Much? bardiferous Jun 2010 Looks like it’s time to swap out a vacuum line. Yep, one was loose. As soon as I reattached it, the engine would start much easier when warm. The idle issue continues - sometimes it seems to idle high, and sometimes it idles low and a bit rough. Will break 200K miles tomorrow. - https://community.cartalk.com/t/2006-dodge-durango-poor-idle-at-startup/131245/7 2006 Dodge Durango: Poor Idle at Startup db4690 Dec 2018 When you cleaned the intake manifold . . . did you replace the gaskets? Misfires and rough idle at startup, but which goes away when warmed up . . . can sometimes be caused by leaking intake and/or exhaust gaskets, which can seal better when the engine is warmed up, because the flat gaskets sometimes swell up as the temperature increases --- Tester Oct 2019 This is not rocket science. Turn the engine over in the normal direction until you see valve action. Then turn the engine over in the opposite direction until you see valve action. That will indicate if the timing chain is stretched. Back when engines had distributors, you’d watch the rotor in the distributor to see how far you could turn the engine before the rotor would turn when checking for a stretched timing chain. But, your engine doesn’t have a distributor. Tester - https://community.cartalk.com/t/rough-idle/50035 Rough Idle bardiferous Jun 2010 Am considering some sort of injector/intake cleaning - either BG 44K, or 3M’s DIY kit. Looking for some feedback. Details: 1995 Toyota T100 Base Model 2WD Std Cab 4 Cylinder 2.7L Manual Transmission Grey, or Gray - not that that matters?! Currently 199,370 miles Right now, I start the T100 cold with a simple key twist & release. Starts 1st or 2nd time when cold, has always started this way. Yep, I feel lucky! When I go to accelerate, even without putting it in gear, the engine kinda bogs down and if I don’t quickly give it enough gas, it will stall. Once it gets to 2500-3000 RPM, it is good to go. It will still idle roughly, but will accelerate without stalling. Some History (from here): http://act…41382.page Ok, so the head gasket was replaced. I’m getting between 19-20 MPG; not bad but have gotten as high as 22 MPG in the good old days. My mechanic has an induction cleaning procedure (static clean of injectors) that he’s offering at around $200. Not sure how much the BG 44K treatment is - but the 3M one is about $50 or so. There’s a YouTube clip on How To: http://www…X5J5kZLTw4 Seeking your feedback… Robert bardiferous Jun 2010 Plugs & fuel filter are brand new and the wires & K&N filter went in last year (7,000 miles ago). It has been starting roughly only when fully warmed up for a few years now. It’s why I replaced the wires last year (with new plugs at that point), as well as the filter. Goldwing Jun 2010 Read the check engine code. It’s probably still stored in the computer. Theoretically, injector cleaning could work IF this is your problem. Not a high probability in most cases though. - https://community.cartalk.com/t/cold-engine-start-and-stall-cold-engine-loss-of-acceleration/113485/2 Cold Engine Start and Stall+Cold Engine Loss of Acceleration Yosemite Mar 2018 JUst a hunch here, but have you looked in the tailpipe to be sure it is not obstructed. I have seen where someone…in the process of backing up…backed into a dirt pile and plugged/partially plugged the exhaust. Partially plugged would allow the engine to idle, but no real acceleration on the road. You could also have a plugged Catalytic converter. Yosemite Saint-Louis-Guy Mar 2018 Have gone through 3 mechanics already-all unable to diagnose the problem. I’m posting here hoping for some input. Tester Mar 2018 Read this. (https://community.cartalk.com/t/2001-mazda-mpv-sputters-at-5-8-tank-full/113821/5) The fuel pump is starting to fail. When the gas tank is full, the level of gas in the tank provides what is called a head pressure. This head pressure assists the weak fuel pump to provide the proper fuel pressure/volume to the fuel injectors. Then as the level of gas in the gas tank decreases, the head pressure decreases where it no longer assists the weak fuel pump. And the engine starts to run rough. Fill the tank, and the engine runs fine. Tester Tester Mar 2018 Take a rubber mallet and bang on the bottom of the gas tank, and see if the engine starts. Tester - https://community.cartalk.com/t/2002-silverado-4-8-cold-start-idle-problem/83480 2002 Silverado 4.8 - Cold start idle problem elkel Feb 2014 After my truck sits overnight it starts immediately and goes to fast idle for a few seconds, then ithe idle starts dropping until it gets to approx. 400 RPM. If I drive off immediately it will correct itself in a short while, otherwise I need to baby the engine speed until it runs on its own - usually five minutes. I cleaned the MAF and performed a MAF tap test with no success. cigroller Feb 2014 I would clean the idle air control valve and check both the engine coolant temperature sensor and air temp sensor. db4690 Feb 2014 @elkel These engines are known for leaking intake manifold gaskets You have the classic symptoms Runs rough after starting up cold, then smoothes out as the engine warms up I’ve seen these symptoms, on your truck, because we have tons of them in our fleet, and I’ve replaced a few intake gaskets, with great success JustAnswer – 4 Jun 07: https://www.justanswer.com/chevy/0q96j-need-copy-gm-service-bulletin-05-06-04-029.html I need a copy of GM service bulletin 05-06-04-029 for a 8 What is GM service bulletin 05-06-04-029 for a 2002 silverado intake manifold leakage? Thank you, - Answered by a verified Chevy Mechanic. Important: Always begin your diagnosis with the Diagnostic System Check - Engine Controls (SI Document ID #(NNN) NNN-NNNN for any MIL or driveability concern. The Diagnostic System Check directs you to the next logical step in your diagnosis. Follow the instructions in this bulletin should the rough idle, misfire, or DTC P0300 diagnostic procedure point to an air leak in the intake manifold gasket. Following the published diagnostic procedures will improve diagnostic accuracy and support our fix it right the first time approach. Condition Some customers may comment that the vehicle may have a rough idle, misfires and/or a MIL illuminated with a stored DTC P0300. Cause The L59 engine is calibrated for ethanol fuel (E85). Due to the low volatility of ethanol, the PCM provides higher fuel flow through the injector, which may pool on the upper manifold to head gasket material. Overtime (usually 12 months and longer), the gasket material may degrade resulting in an unmetered air leak. Correction Replace the upper intake manifold gaskets with the teal green gasket material, P/N 89017589. Important: Do not replace the upper intake manifold gaskets with the original orange gasket material, P/N 17113557. asemaster Feb 2014 I agree that you have all the indications of a leaky intake gasket set. Only takes a few minutes of warming up to get them to seal up and the engine starts to run properly. - https://community.cartalk.com/t/car-shuts-off-when-warm-white-smoke-from-exhaust/82766/31 Car shuts off when warm, white smoke from exhaust George_San_Jose1 Dec 2013 The “A” in MAP stands for “absolute” rather than “air”. A car’s MAP sensor uses a silicon sensor to measure the intake manifold’s absolute air pressure relative to a total vacuum. This makes it possible to use the MAP as an altimeter, so the car’s computer can compensate the fuel/air mixture as altitude changes, like when driving in mountains. If you happen to come across a discarded MAP sensor, check to see if it works before throwing it away. If it works you could use it as a DIY altimeter, or as a barometer to predict the weather. - https://community.cartalk.com/t/car-shuts-off-when-warm-white-smoke-from-exhaust/82766/43 db4690 Dec 2013 @SOTF So the problem is finally resolved? No more stalling when warmed up AND the engine idles well? So the bad idle was the leaky intake gasket? And the stalling when warmed up was the crank sensor? SOTF Dec 2013 db4690, correct. However I am now facing a different problem. The car has become progressively harder to start. Now it will not start without starter fluid but runs fine once that happens. I will be posting a new thread on this but the other things are correct and I believe unrelated. The bad idle was a result of a blown out intake manifold gasket. This fixed the rough idle. A new crankshaft position sensor fixed the car shutting off when the car would warm up and then would not start until cooler. Revving kept the engine alive but when no throttle was given the car would take a death plunge and shut off then not start until cooler. - https://community.cartalk.com/t/1978-chrysler-aspen-running-rough/119291/14 1978 Chrysler Aspen running rough Mustangman Jun 2018 --- Ethanol does attack nitrile rubber commonly used in older cars for fuel lines, fuel pump membranes and carburetor parts. The higher the percentage, the more aggressive the degradation. Your '87 truck will, at some point have problems from running modern gasoline. Stock up on fuel pumps, filters and carb rebuild kits if you plan on keeping this truck running. - https://community.cartalk.com/t/96-saturn-sl2-high-revs-clicking-temp-clunking/84912/4 96 Saturn SL2 - High Revs, Clicking Temp, Clunking keith May 2014 --- There is another issue that plagued the 00-02 SL1 engines and that was the intake manifold gasket. The design on the SL1 engine is very weak around the #1 cylinder and in 00, they went to a cloth gasket instead of a metal backed gasket and it would fail regularly. I have not heard of this issue being so common on the earlier SL1 engines, though it would happen on high mileage engines occasionally. I have not heard of any issues with this on the SL2 engine but some of your idling issues are symptomatic of the intake manifold gasket or other vacuum leak. These engines are not prone to blowing the head gasket unless severely overheated, but it can happen if the coolant gets way too old. The frothy coolant is worry some though. I’d start with a genuine GM ECT sensor and connector first. keith May 2014 Don’t “flush” the cooling system, especially do not use any chemical flushes on a Saturn, that is asking for trouble. Just drain the coolant from the radiator and the block. The block drain is just under the lower radiator hose, but if you are going to replace the thermostat, you will be removing this hose anyway. You can stick a garden hose in the upper radiator hose with the thermostat out to flush the block, but I do not recommend it. I prefer to just drain the whole system and refill with fresh coolant mixed either 50/50 with distilled water, premix (already diluted to 50/50 with purified water) or my favorite of 2:1 antifreeze to distilled water. Any residual old coolant will actually have less contaminates in it that tap water. --- - https://community.cartalk.com/t/pcm-update-needed-or-just-guessing/73724/16 PCM update - needed or just guessing? keith Jul 2012 If you do have a cylinder with low compression, it will probably be due to a burned exhaust valve, not rings and certainly not valve guides. You have the 3.0 engine which I believe is a Mazda engine, not a Ford engine, so it may have solid lifters. If it does, you should at least check the valve lash before doing anything else.