I have a 92 firebird with the 3.1 in it.

starts right up in the morning, cold idle goes then it slowly comes down to operating temperature and rpms. when its trying to go to an idle It goes up and down up and down only like a couple of rpms feels kinda like a slight miss.

I pulled the plugs all of them are the same and burning good. I have cleaned the iac and put a new temp sensor, (on the intake by the throttle body). new plugs cap rotor, ignition module. and reset the ecm and still have the problem. I have found no vacum leakes can't hear any and I used the old propane trick to test.


Any help would help lol.. ruff idle only when warm when I hold the rpms at like 1200 it tends to bounce like it will catch and drop back down but my foot dont move. but the higher rpms it runs smooth>>???

 

Maybe the o2 sensor or a small vac leak.

 

When you reset the ecm did you do the idle relearn process?? If not do that and see if that helps. Google "idle relearn V6 thirdgen" and you'll see many threads on it.

 

My 94' cavalier is pretty much bone stock with new plugs and wires and when it warms up and idles down the idle is a little rough, but i think it is normal. The car doesnt have any performance issues and doesnt use any oil still greats great fuel economy around 28 city. I just got used to it i guess.

 

I take it you're not getting any trouble codes since you didn't mention it. Check your MAP sensor and I had to check all my vac hoses individually with vacuum pump to find my leaks. Good luck and don't forget to do that "idle relearn".