When I first got the Jeep, I had problems with it idling correctly. It had sat for awhile. I first replaced plugs, wires, distributor cap, rotor and coil. Still had problems. Then I replaced the idle air control valve and helped alot. When I would shut off the engine, the IAC would then open the throttle body. So, when starting it would act normally, stating at about 2 grand and then falling down to just below 1000. Now, it does not do that anymore, except occasionally. I have no idea why. Thus, I am guessing the problem could be in the ignition control module or the ECU. I can have the ICM tested at Autozone. If that is okay, then I'm guessing the issue is the ECU. It starts up and runs okay besides the issue mentioned above with the IAC. But, somedays it will idle way down at 500 and die and other days it will idle at about 800 but will fall down to 500 or less and then pick backup to 800 or so about three times, then be fine. Strange
Ok, this is the post you sent. When you replaced the Iac did you also clean the the throttle body and IAC passages? High idle is usually an indication of a vacuum leak. Check for vacuum leaks and remember that you have vauum lines running to your axle and you heater controller in the insrument panel.