crookedbowtie

My car is idling high. I have been over almost everything. I pulled my IAC and cleaned it and its home with carb cleaner. I checked resistance in the terminals..within spec. Continuity in the wires to PCM A OK. No DLC codes. The actual part itself is questionable. I couldn't get the pintle to move at all until I cleaned it and put pressure to it. It will free play 1/16-1/8" and I don't care how hard you press on it it won't move any more. Is this part good or bad????

2002_Z28_Six_Speed

iTrader: (19)

Check for checks in your emissions tubing. Those can crack with age.

All Black SS

You should pull the pcv hose off, plug it and see if idle changes, pull the brake vacuum booster off and put your finger over the hose end. The PCV hose tee at the back of the engine rots and if it leaks can suck in air.

The IAC sounds normal for what you're doing to it.
If you plug it in with it out of the throttle body, the pintle extends to try to lower idle, with it not installed it will extend and fall out, ruining it.

About the easiest way to trouble shoot the IAC with no special tools is to unplug it and remove it, plug the hole in the throttle body where the pintle seats in so it's vacuum tight. If it idles lower, too low, or dies, it's probably bad.

crookedbowtie

Already checked for vacuum leaks, it is in a swap. All hoses are new and I have already double checked.

crookedbowtie

No emissions what so ever present. Block off plates are sealed, no vacuum leaks.

I pulled the IAC....diiirty! I cleaned it, still idled high. I pulled it out again to see if I could move the pintle at all. No way in hell it was completely froze up. Tore it apart and the bearing was rusted up and everything else was stuck, didn't throw codes and it passed a resistance test though. Bought a new one for a 95' although mine is a 96' ( have to order the 96', the 95 is cheaper looks the same and available, but has a diff number that doesn't cross). Any reason why it won't work properly on a 96'.

All Black SS

I have a box of IAC motors. One day I went to a junkyard and pulled every GM one I seen. A lot out of 4 cly fwd GM cars. Very few have different shaped pintles, some are 'clocked' different (relationship between bolt holes and wire plug).

Now on to the diagnosis. Why did you do everything EXCEPT the most revealing test?
If you plug the pintle hole with anything, a finger, and the idle goes real low then you found the problem, no doubts, no further questions, no dicking around trying to get a crusty old IAC to work. It's just too easy.

RCowan

iTrader: (25)

Carb cleaner or brake cleaner sprayed directly on the IAC can clean all the grease out of it causing it to lock up or worse, strip the gear inside...I know this...from experience. If you have scanning software make sure it is moving around constantly while the car is running. If its ok, look for a Vacuum Leak somewhere.