Question about Cars & Trucks
02 Monte Carlo SS 3800 SERIESII V6, no mods. Replaced MAP, IAC, TPS, ECM, Air Filter, Ignition module. No codes! Engine wants to idle from 1500 to 2300 rpm. If I am cruising at 1800 rpm and take my foot off the gas, the engine stays at 1800 rpm and the car almost drives itself. If I mess with the intake before the throttle body it will run right for a couple of miles then goes back to idling hi. Never seen this before. Please help
Try this. Get a spray bottle of water and mist the area with the engine running. If the RPM changes or it stalls, you have a Vacuum leak in that area.
I am not sure what you are touching to temporarily solve your problem. You may have a bad throttle position sensor or a part called an idle speed control solenoid.
Now some makers use split level intake manifolds which have 2 chambers. They are switched by Vacuum or Electric solenoids.
It sounds like you are getting extra air into the engine, which is the same thing as opening the throttle. Spray the water around Vacuum solenoids with the engine running, if one is cracked , it may draw air. Check your EGR valve for venting.
I hope my solution helps you.
Posted on Oct 25, 2012
Sounds like a faulty mass air flow sensor.Try spraying the small thin wires with a nono-chlronated brake cleaner then let it dry for 10-15 minutes then re-install.Make sure to reset the computer whether you clean it or replace it with a new one.
Posted on Oct 25, 2012
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Posted on Jan 02, 2017
SOURCE: buick lesabre nightmare
Need to get a scan tool and look at the data stream while it is running for alot more info.Also any trouble codes.Sounds like initially,the engine isn't getting any fuel.I would have a pressure gauge connected to the fuel rail on the engine,so i could monitor the fuel pressure while all this is going on.Items to look at on the data stream would be timing,what timing is the PCM commanding for the engine.Also,have you checked for continuos power feed to the coils during this no start condition,and fire at the plugs while cranking.You could possibly still have spark,but maybe it is extremely weak?I have seen bad ignition switches cause weird problems before too.Many things power up through the ignition switch,just a thought.Have also seen bad PCM's cause strange problems..38 volts is a little on the low side for GM.Usually see those at,at least .50 and up,and rise steadily while pressing the throttle,up to just under 5.0 volts.Potentiometer with 5 volt supply.Vacuum leak can be checked with engine running at a steady idle speed,spray brake cleaner all around the intake manifold and listen for engine speed change.
Posted on Jul 31, 2008
The PCM controls idle speed to ensure good driveability. The PCM will only attempt to maintain the desired idle speed when it “knows” the throttle is closed. A throttle switch or the TPS input is used to determine when the throttle is in the idle position. Motors and solenoids are used by most PCM’s to control idle speed. Many PCM’s are programmed to attempt to control the idle speed by adjusting spark timing and then by controlling the idle speed actuator. Some computers of the early 80's did not control idle speed.
Posted on Oct 19, 2008
SHOWING MISFIRES ON SCAN TOOL?IF NOT,ENGINE CONTROLLER HAS NOT LEARNED MISFIRE MONITOR..WILL HAVE TO BE DRIVEN A BIT FOR RELEARN..IF YOU CAN SEE MISFIRES..MISFIRING ON MORE THAN 1 OR ALL CYLINDERS?CHECK UNDERSIDE OF IGNITION COIL FOR CRACKS..IF NOT CRACKED,YOU MAY HAVE A FAULTY CRANK SENSOR..ANY CORRODED PLUG WIRES AT DISTRIBUTOR CAP?ALSO CHECK IF ANY OIL PRESENT IN INTAKE MANIFOLD..GASKET ON BOTTOM OF INTAKE MAY BE BROKEN CAUSING AN INTERNAL VACUUM LEAK
Posted on Jun 22, 2009
SOURCE: 1999 vw cabrio engine cuts out
I had the exact problem with my wifes 99 Cabrio - parked for 9 months. Ended up having to have the shop reprogram the ECU - it then worked fine.
Posted on Aug 20, 2009
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