I come to the great collective as a confused man. I have a '92 with the 4.0L engine. Engine cold, engine warm, it doesn't matter. When I start up, the engine idles fine. By the time I've driven 3 miles, at varying speeds, the idle is up to 1800-2000. If I shut down the engine for 15 minutes and then restart, it idles at 650-800 just like it should. Until I drive a couple of miles, and it goes back up. If I run down the highway at 65 for awhile, the idle is above 2000, close to 2500, and stays there until the engine is shut down for that same 15 minutes. I changed the idle air control, and actually read and followed the enclosed directions for installation, but the problem persist.
Is there some secret reset button I don't know about?
Anybody got a suggestion where to go next?