Roler

Can you maybe free it up, or pull it out more (gently) manually to check if it even could come out more?
I can imagine that if it doesnt protrude far enough, the idle will be higher

bluejeep2001

That part that sticks out of the motor/ into the throttle body rotates and extends in and out. The further out it sticks means less bypass air...so lower idle. As you need to compensate for load...more volts from alt or ac engaged...the iac motor retracts the arm allowing more air to bypass the closed throttle plate and more rpm. The computer senses the idle speed and if its lower than what it wants it sucks in the shaft and idle increases. If too high it extends the shaft and idle lowers. All done automatically by the pcm to keep your idle between 650-725 under all conditions. In theory

92SmokyCherokee

I'll try it. I'm pretty sure that it's the wrong part though.

Thanks for the explanation of how it works. That would make sense that my part being too short for would cause the idle to be way too high.

92SmokyCherokee

So it appears that the o ring did not solve the new issue of a higher than normal idle and slow drop to idle when coasting. I also looked on Rock Auto for a iac with a longer plunger thingy and they all look shorter than my original one.

92SmokyCherokee

I couldn't get it to come out any more.
If anyone has run into this before, what did you do to solve it? Do the '92s have a different part? Seems unlikely since it is the same 4.0L engine.

Roler

You could quickly check on Rockauto to see if they'd list different part numbers. But I doubt it, since it's the same 4.0 and I've not come across info there was a significant change in any IAC's over the years

Roler

I just went over the entire thread again

Have you replaced that square gasket yet?
And your throttlebody gasket, how was that?

And could you go to a partstore near you and compare your old IAC with what they have available?

Have you verified your TB valve is closing fully at idle after cleaning?
Have you checked TPS at idle?

These are things to check as well because they different causes for high(er) idle.

(Vacuum lines all connected?)

I'm positive it's something that can be solved easily.

92SmokyCherokee

Throttle body gasket is new.
I have not replaced the little square gasket yet because I don't know how to get one without buying a new throttle body.
I have not compared the IAC valve with others in a parts store, but that's an excellent idea!
How would I verify that the throttle body is closed at idle. I haven't done anything with the TPS yet, I might go ahead and replace it. My brothers XJ had issues with the TPS going bad, but they were different from what I'm experiencing.
I don't see any disconnected vacuum lines, but I'm still figuring out where they all are.

Roler

Don't replace the TPS just yet.
You can measure voltage at idle on the tps, to see if it corresponds with what it should be at idle. As a verification.

The TB valve should be closed shut at idle. Since you've cleaned it, I assume there is no build-up around the walls or the valve surface itself that would prevent it from fully closing.

I do wonder if missing that little square gasket that broke, is allowing any 'false' air in

92SmokyCherokee

Just thought I should update y’all. The Jeep is idling fine right now, except sometimes when I turn it on it idles at higher rpm than it should for a while. I haven’t done anything else with the IAC or TPS so I guess it fixed itself lol

Roler

Thanks for a comeback

I don't believe in car problems fixing itself but if its working good enough for you atm, just observe.

It idling higher than normal, you mean other than on cold starts?

92SmokyCherokee

You’re welcome, it took me long enough lol

I don’t really either but if it works good enough for me to drive I don’t really want to mess with it. Once I touch it there’s a 50% chance it will end up in worse shape than when I started lol

I would say it happens predominantly on cold starts.