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Fast Idle on 2000 Cavalier

The motor idles at 1500 (1800 w/ AC on). When coming to a stop, the trany in neutral, the motor revs up around 3500 to 4500. The OBD codes suggested a vacuum leak or O2 sensor. I have replaced the O2 sensor, no change. I have pulled every vacuum line from the throttle body and covered hole and no change. I have even replaced the idle control solenoid, no change. I have even bathed the vacuum lines in CarbCleanor when the motor is running to find a possible leak, nothing. I am at a loss. A mechanic friend said he would do the exact same thing I would do to find the problem, so there is no use for me to pay him to mess with it when he would do the same thing I have already done. What can I do to find this problem?

Did you try spraying ether around the intake manifold gasket(s)?

Yes, I sprayed all around the intake manifold gaskets, evap emission canister, that pancake looking valve I think called erg. On a wild hair, I returned to Autozone to have the OBD codes re-read. There was a new code about the throttle control problem. The guy asked if I reset the computer since replacing parts. No. He used the computer to clear the codes. After that, the car would not start or run unless accelerator is applied. We put on the old idle control, and the car started and idled at 2800. The part guy went back and got another idle control off the shelf. After playing with it, we realized the first new idle control didn’t work. After 45 minutes, the car idles 700 to 1000, no check engine light, no racing motor at stops. Lesson 1: some parts come new, but don’t work. Lesson 2: OBD codes gives clues, not answers (codes told of O2 sensor or vacuum leak, in end, it was idle control solenoid). Thank you for your interest and help.

It’s called an EGR (exhaust gas recirculating) valve.

Glad you got the problem fixed. Yeah, the codes are only hints, finding the actual cause can be a lot more of a challenge. Especially when you get a defective part in.