IAC Questions

I want to clear something up about my IAC module.

First, am I correct in deciding that it was the module mounted on the left side of the throttle body (when looking head on) on my 1990 XJ. The one on the right had a little lever on it that rested under another lever that turned the "air intake plate" (for lack of correct terms). That led me to decide the other was the IAC.

I have read a lot of threads that said the IAC could be dirty and sticking open or sticking shut. I took it off and it doesn't look dirty at all to me.

All I see is a goldish "cap" with a rubber bullet shapped rod with a metal cap on it sticking out of the goldish "cap." Y'all with me so far?

How can I tell if the IAC is bad? Should that rubber bullet be moving or not. I can't make it move by pulling it, pushing it, or turning it.

Any input would be appreciated.

Thanks

This is funny...that is the IAC but I have the same questions as you.

I pulled mine off last night while doing a "bench" cleaning of my throttle body. My TB was really dirty.

I couldn't make mine move either but I was afraid to try to hard for fear of breaking it. My guess us there's solenoid inside that works off of a voltage send by yet ANOTHER sensor. The signal causes the IAC to extend or retract the "bullet" thus affecting airflow...

That's my guess anyway. I spent 1.5 hors cleaning the TB and IAC carefully....and noticed NO IMPROVEMENT in my idle.

The idle speeds moves around a couple few hundred RMAS so and I can't figure out why. I've traced evey vac hose and cant't find a leak.

The AIC consists of the stepper motor with the pintle(rubber bullet) attached to its shaft, and the bypass passage, covering the pintle, which is screwed on to the motor body.

It's that passage that gets dirty. If you haven't detached it from the motor, do that -- then really clean it out.

TRY NOT TO ROTATE THE PINTLE...(MUCH) !!

The ECM controls idle speed. There are 4 wires going to the IAC--2 used to extend the pintal, and 2 to retract the pintal. It's a digital signal that can be seen with a light emitting diode test light placed across either pair of wires.
Blinking lights indicate communication with the computer, but does not mean the computer is sending a good signal. The dealer has a "box" that allows the IAC to be cycled independent of the computer. Generally, it's a dirty pintal seat in the throttle body that keeps the IAC held open, resulting in high idle.

What should I clean it with?

I just brush or scrape the crude of of the piston and the seat, then put a drop of oil next to the piston and let it run behind the piston by gravity. Word of warning, don't try turning the key on with the IAC removed and the connector connected. I got curious and launched my piston half way across the driveway. They say in the book, once the piston is seperated from the motor, it's junk. There is a threaded rod behind the piston, that is coverd in grease, that runs into the motor.