90 cavalier engine running rough

well to start of i got the car from my parents. it has 230,000 on it. it has a 2.2 with tbi with auto trans. it had a bad coolent sensor in it that made it run high idle and rich. which hey drove for a few days like that. since then its been replaced. had no ses light. i've been driving it since then and it has a rough idle when cold. once driven for 30 mins its smooth and drives great. recently its starting to want to die. i let the car warm up for 5 mins, then take it out and under light acceleration it runs but then starts sputtering and then recovers and continues this until i let off. havent seen any smoke from the rear of the car. no ses light. it seems to keep getting worse. new plugs,wires and air filter done about 4,000 miles ago. about 34mpg hwy. cat was replaced once about 1 year ago. any ideas?

may need an air induction flush (BG makes a great kit). At least clean the TB out really good, that will help some.

i just put ina can of sea foam so i'll see if that does anything.

no ideas?

seafoam really doesn't do much. At the very least clean it out with a rag and a can of TB cleaner.

ok. i'll try it sunday. i played with it today and i can rev it up just fine. just only when its under load it does it. even power braking it wont cause it to happen.

clean throttle body with no luck. still does it. swapped out ecm and still doing it. also i noticed now if i come 2 a stop light and put it in neutral then it idles fine, then after about 10 secs it revs up as like someone tapped the gas but then comes right back down. it might go to 2,000 rpms or so. i dont have a tach. then runs for a bit more and then does it again. and it continues to keep doing this. light throttle is when it runs bad. 50% or more and its fine although you can feel it slightly miss every now and then. i'm running out of ideas. also changed o2 sensor with no luck. i know for a fact its not the tranny.

Check the TPS, be sure it reads right in the range where it's running poor.

how can i do that? and is there a scale somewhere i can go by? why would it only do it when its cold?

how can i do that? and is there a scale somewhere i can go by? why would it only do it when its cold?

Two ways, I would do the first(if you have an OBD-I scan tool). 1- Connect a scan tool and watch the TPS reading as you move the pedal from 0-100%. It should go up smoothly, but may not necessarily go from 0-100, my '04 reads 8% with the throttle closed, and 87% at WOT. The second way is with an oscilloscope connected between the sensor output and ground. The signal should go up smoothly between 1 and 5 volts.

The TPS is just a potentiometer, it is possible that it's worn down at the lower end of the sweep just enough to not quite make contact. It is a long shot, but when everything else checks out, you gotta start checking anything that can cause the problem.

well whatever it is its getting worse. i went to drive the car yesterday and it wouldn't stop doing it. now it does it 3/4 and less. i ordered a new tps it should be here this week.

Good luck with this issue. My 96 Sunfire is also starting to have some idling problems. I'll be keeping an eye on this thread.

well today the sensor came and i replaced it. still no luck. although today it was worse then normal. so today i saw smoke from the rear when it was sputtering. i also tried replacing the fuel filter with still no luck. anymore ideas?

Have you checked the fuel line/injectors? Just throwing ideas out. It does sound like something's sticking just not sure what. I'll definately ask around for ya.

well it only has 1 injector. its tbi. and so far the guy i have working on it has narrowed it down to one or both of the coils or the ignition module.

replaced both coils. one of the coils had a crack in it. so far all is good. also replaced the spark plugs with ac delco plugs. car runs a lot better.

Glad to hear things are looking up. Keep us posted on if this is a permanent fix.

well its still working!