High Idle

I have a 90 XJ AW4 and it consistantly idles at acout 1200-1300 RPMs while in park or neutral. I'm pretty sure that it is not the IAC since i repaced that and cleaned the hole about 3 months ago. I want to get that idle down since it makes my jeep heat up quite a bit stopped in downtown traffic. Any Ideas?

-Josh

High idle is a symptom of a vacuum leak. A vacuum leak will also cause it to run lean at idle and that will cause it to run hot.

How might I go about finding such a leak.

To check for vacuum leak: Spray suspect vacuum hoses with chemtool, a cleaner that can be found at your local parts store. Caution, this stuff is flammable, and you need to be careful to wear eye protection. Also, be careful not to give the IAC or the TPS a direct blast. They tend to not do so well against moisture of any kind. A small vac. leak will cause a rise in RPM from the chemtool, and a large leak will kill the motor.
Often overlooked... be sure you hit the bottom side of the EGR valve when you are checking for leaks. Common place, and most people stop with the rubber hoses.
If nothing turns up, you may want to rethink checking your IAC.
Another consideration may be overfueling due to the O2 sensor. If you want to rule that out, the resistance between the black/tan and black/dark green wires should run from 5-7 ohms. Out side shot, but easy to check.

Best of luck to you...
TheRasper.

I have experienced this too on my '90.Mine turned out to be the linkage below throttle body binding.There was a metal clip that got bent not letting my linkage return to idle completely.Easy to rule out,manually push down on linkage,if idle dies down to normal there you go.Hopefully it will be that easy.