I have a 1990 XJ with the 4.0L, AW4, and 231 TC.

The idle is all over the map. When I start the Jeep it idles at 800 rpms the first couple minutes. Then it is up to chance where it idles from there. Anywhere from 400 - 1500 rpms in neutral. Last few days it has been mostly around 1500 rpms.

Today I pulled the throttle body and cleaned it. Cleaned the IAC too. Started the Jeep and it idled at 2500 rpms (after adjusting the TPS). Shut it down and immediately started it back up, idled at 800 rpms. Took it for a quick drive, idled at 800 half the drive, then 1000 the other half.

I'm beginning to think the IAC is going bad, but I am unsure how to test it. I read the FSM and it says to use an exerciser tool. Thats not an option. Other methods?

 

I'm not sure this will apply to a '90 XJ, but if you're into testing give it a try.

 

Of my Tips, how many have you completed?

Which method did you use to adjust the TPS?

 

I've completed 1, 3, 5, 7, 8, 11, 31, 34, and 37. Set TPS as per instructions on your site. You may recall I had a thread about it slow to start and idling rough. Got it running good now with exception of the rpms all over the map.

 

Ever replace the tPS?

 

Yes. Brand new, maybe a week old. New plugs, cap and rotor too.

 

Maybe you should do this:

http://cruiser54.com/?p=94

 

Will do next time I'm under the hood. The .003" clearance, is that between the set screw and the throttle linkage? Or between the butterfly and the throttle body bore? Thanks again.

 

Butterfly and bore.