I have a 93 Lumina and it just started this rough idle and when you stop the RPM's stay at and 1500. Usually the car idles at 1000. If you crank it sometimes it will idle fine, but sometimes it will idle at 1000 and you can just sit in the car and not touch anything and it will just idle up to 1500 on its own, and the SES light will come on. When that happens you can drop it in to gear and it will come down to 1000 RMP and the SES light will go off.. You can put it back in park and it might idle fine but the agian it will idle back up to 1500 and the SES light will come back on..(ITs crazy) The AC is off so no its not the computer telling it to idle up. We own our own car shop and i checked the codes it was code #35 idle senor. I changed it and it did not help. Also the car has a little miss between 1000 - 2000.. smell like its running rich..

The car is just our fam's spare car but still it needs to run a little better.. The car runs great and it has good horsepower, but it's the idle that kills me..

If you have any ideas please reply.. Thanks

It's either the IAC valve or its wires/connector. The valve is reducing the air flow, which makes the combustion gas richer. This explains the high idle. Another possibility is a faulty ECM but I will first check the IAC valve.

Yea i changed the IAC and it is still doing the same thing. I will chek the wires but it proably is the ECM...