I have an issue with the idle on my 1985 L98 Vette. my idle varies between 450 & 1000 RPM's I've checked my IAC count with a Tech 1 scanner and my count is at 85, I know it should be between 20-40 IAC counts however adjusting the idle speed has no effect on the idle or IAC count. I believe the problem may be a vacuum leak and I'd appreciate any suggestions as to how to find this leak or and any other ideas on how to resolve this problem.

Thanks,

Ed

Have you tried the throttle positioning sensor(TPS), manifold absolute pressure (MAP) and the mass air flow (MAF) sensor? The last two sensors are on the right side of the intake manifold and sometimes the small hoses attached to one of those sensors crack with age. All of the sensors are available and the hoses replaceable. If you replace any of the sensors you may want to disconnect the battery to clear the computer. Good luck and have fun. 

Hi Bob,

Thanks for taking the time to respond and for your input. My Vette is a very low mileage car with less than 30K miles and is stored in a heated garage so the hoses look good, however I will look into the hoses you mentioned. As for the sensors I was able to borrow a Tech 1 scanner and reset the TPS to the proper voltage, but I didn't have any trouble codes. Last summer I replaced the IAC valve and gasket, so I believe that's good. I also checked all the fasteners on the throttle body which were all tight, I may replace the gaskets even they also look good.

Regards,

Ed