90 cavalier 2.2 tbi missing

[metallica21156]

i have a 90 with about 234,000 miles on it. the issue i'm having is during warm up and has to be 100% cold. or sit for at least a day. i start the car and everything sound fine. idles up and slowly comes down just like it should. then al of a sudden it starts to sputter and runs rough. i can tap the gas and it revs up and then idles back down and runs rough again. without touching the gas or touching the gas it sputters for about 1 min or so and then runs normal again like nothing happened. i've done complete tune up including fuel filter. rebuilt the throttle body. replaced egr,map,tps and engine coolant sensor. any ides? no light or codes.

[J-Ri]

Check out the O2 sensor. I've seen a few cars that start up and run fine until they go into closed loop (uses sensor feedback) and then the PCM sees very rich or very lean from a bad O2 sensor and they start running bad. O2 sensors also need to be at a certain temperature before they start working, yours may just need extra time to heat up before it starts working.

[metallica21156]

replaced o2. still doing it. now as it has gotten colder it has gotten worse. now i start it, it revs up to a point, starts sputtering hold theres for a few seconds and idle drops down runs smooth for a while then sputters again for about 10 seconds, then smooths out and acts like it never happened. any other ideas? i've tried a new ecm and a new prom chip. still no change. any ideas?

[J-Ri]

Man, you have some bad luck with cars. I looked back through your posts to find the last one to see what all you did and I suggested, but couldn't find it (due to poor, but free , wireless connectivity and lack of patience). I did throw my in on your Blazer's problems.

See if your friend has the GM1 adapter for the MT2500, you'll probably just have to look through the datastream and look for anything out of whack. Measure the resistance/volt drop of wires/grounds, confirm scan tool readings. I really don't know what else to do.

[HannabilRox]

I have a 1988 Cavalier wagon 2.0L with this exact same problem. It just started a couple months ago even when the temp outside was still in the 60's. When you first start it and try to back out of the driveway, it sputters and stalls. Restart it, and it runs beautifully the rest of the day. It is too cold to go out and mess around with it right now, so I just have to start it and let it warm up a bit before driving it. Not sure, but is there some kind of "cold idle circuit" in these cars? I know that when you either turn on the headlights or put it in gear when first started, the idle does go up, or at least attempts to go up like there is an "idle up" circuit. Wagon has 155,000 miles on it and runs like a dream other than that. New parts include, fuel pump & sending unit, timing chain, wires, plugs, TBI injector, exhaust ( complete ), water pump & anitfreeze, all hoses. Will be interesting if any of us figures this one out! Keep us posted!

[J-Ri]

The "cold idle circuit" is all computer controlled and based off the ECT sensor, which I believe he said previously was good. It uses the same injector, just commands it on at a higher duty cycle when very cold and opens the IAC valve a bit.

[metallica21156]

well what ever it is for mine its getting worse. now it does it longer. then the other day i was driving the car and after a 20 min trip i was coming to a stop light and it almost died on me. put it in neutral and tapped the gas it recovered and off i went with no more issues. the only other thing it does is the if you floor it after idling for a bit or like coming off a highway it hesitates and then speeds up. i always thought it was just because its tbi but who knows. i'm starting to wounder if its not the ignition module on the back of the motor.

[metallica21156]

still no other ideas? now that its warmer it starts ok. but even after warmed up if your trying to pull up a hill real easy you can feel as almost as if he engine is missing but its not running rough. but you can feel a loss of power. give it more gas and it goes away. when i put the a/c on its even worse. then it feels dead unless your more then 1/2 throttle. i had a friend of mine change out both coils about 6 months ago. it ran something like this but when it was damp out it missed really bad. then it quit and stated missing bad even at idle. so he swapped them out. just the coils. not the module. could it be this module taking a dump? it also idles a little rough but you light rest your foot on the gas and it smoothed right out. any other ideas what this might be? as far as reading on the scanner the look ok. no ses.