Ok, so here's the scoop (92 z28 5.7 tpi auto trans) car ran fine no problems. over the weekend I decided to replace the O-rings on the fuel injectors (22lbs Bosch III) because I've never replaced them since I bought the car 5 yrs ago, the O-rings were dry and brittle. Put new ones on, put everything back together, fired up the car it idled nicely(7-800 rpms). I let it warm up, and when it got hot (normal temperature) all of a sudden rpms went up to 1300 rpms and wont idle down unless a put it in drive or reverse. I turned off the car and turn it back on and the rpms stay at 7-800, but within seconds rpms go 12-1300 every time. I didn't see any problems visually like disconnected hoses or fuel leaks. It idles fine cold, and idles high when it reaches normal temperature. Also, FPR diaphragm was replaced. Anyone know the solution to my hot high idle if you will.

 

If the IAC is disconnected before the engine is restarted after reaching operating temperature, does the RPM still increase uncontrollably? Learning that may help determine whether the problem is mechanical or with the engine controls.

 

You could always spray some carb cleaner and check for vacuum leaks where you were working. You had to take apart your TPI to get to the injectors correct?

 

Thanks for your info. The idle is fixed. I don't know why or how in the world the IAC become out of adjustment. I reset the IAC and it was all good again.