hey everyone i have a 97 z28 lt 1. i just got the car back from the shop had plugs,wires, pcv valve, waterpump and fuel filter. car runs great except the idle is all over the place. while parked it goes from 600 upto 1200 then back down. ant idea what it is? i am taking it back in tomorrow.
thanks

 

throttle position sensor? vacuum line unhooked?

 

add to ^^^ idle air control valve. has it been scanned for trouble codes?

 

per some ones advice i unplugged the iac and it maintaind a steady idle but it was high around 1300. also what should battery voltage be and alternator output be

 

try cleaning it. could be sticking. could also be failing. best to get a iac noid light and see if the flash count is constant or jumping from fast to slow. if its steady then i would suspect a bad or sticky iac.

 

thanks craby. what should battery voltage be and alternator voltage be? my battery was 13.4 volts with the engine off. when i started the engine it was up tp 15 volts. i checked with a digi multi meter at the terminals

 

wow 15 volts is high. 13.2 is stock running volts but a 12 volt battery will handle up to 15.5 when charging. not so sure of your sensors and lights though. when u do run a battery that high it will shorten its life. what kind of battery? what alternator? i like the 13.8 to 14.2 range. as soon as my current stock alt goes thats what ill be looking at.