I have a 1994 Corvette. Lately it has developed a problem. When I’m stopped at a light, the RPMs surge from about 500 up to 1000, and then drop back to 500. If I shift from Drive to Neutral to avoid having to keep my foot hard on the brake, the engine will momentarily surge even higher to about 1500.
Anyone have any ideas what might be causing this problem?
I would first look at:
[list]Idle Speed Control,[/list]
[list]Throttle Position Sensor,[/list]
[list]Carbon deposits on throttle plate.[/list]
Vacuum leaks are notorious for causing fluctuating idle speed.