High Idle RPM, 1990 ZR-1
 

I have a 1990 Zr-1 with 112K miles on it. I had a local Chevy dealer put in a new radiator about 2 weeks ago. The car ran great. The other day, I drove the car and noticed that the idle RPM was high (1500 vs. 800). To lower the RPM, you have to "kick" the throttle for it to come back down. I looked under the hood, and found no vacuum lines detached. I did notice that there was a small air filter missing from what looks like a air pump of some sort. Could something get sucked into the vacuum system that could be causing this?

Dave:What do you mean by a small air filter missing ??I do not recall evert see a small air filter,my guess for your high idles is the wear on the bushing of your trottle body butterfly wich gets stuck unless you kick the trottle pedal. If you removed the intake accordeon and the horn of the trottle body you may be able to see if you have to much play on the butterfly especialy the passenger side.

Also with that many miles my bet is the back of the throttle plates are all gummed up. Get some brake cleaner and clean the front and back of the throttle body plates. My guess is they are sticking. Only other guess might be the IAC valve on the side of the throttle body.