I have an 87 Z28 305 5 Liter. I replaced the IAC due to a low idle. now it is idling at anywhere from 1400 to 2100 RPMs. I tried replacing the TPS and it made the high idle even worse. Could me forgeting to take the negative battery cable off when i repaced the IAC have caused this? i did take it back off when i changed the TPS and it was off for like 10 minutes. I tried adjusting the torx screw where the throttle is and after reversing it a little the brackt wouldnt come back to touch it. i returned the torx screw to its original position and nothing has changed. Temp gauge not working either since before i ever bought it. HELP!!!!

 

before I get too into it read the technical article on this site on how too adjust the TPA and IAC valve and try these. If you already have, Sounds like maybe you left something off after you did the IAC swap. A vacuum leak will make you idle high. Look and make sure all your vacuum hoses to the throttle body are in tact and in good shape. Also make sure you tightened the IAC corectly. Don't go nuts but make sure it is snug. Also did you take the?throttle body of when you did the swap?

 

I only unplugged the IAC sensor. i forgot to unplug the negative battery cable. i then replaced the IAC sensor and when i was putting it back on the harness started falling apart like it was dry rotted. only one of the four plugs still has the shroud around it but it is back inside the new IAC.