Ok, So I've searched the forum and found a few things pertaining to WJ high idle in the 4.0. I just want to pass by you guys what im dealing with just incase. 2004 WJ 209,000 miles on it. When I first start it in the morning the idle is 1,600 RPM. I can go out side and disconnect the positive batt. cable and touch it to ground for 60 seconds, Hook it back up, I go inside and turn the headlights ON then OFF twice. I then start the jeep and it idles around 800/850 RPM. I drive it to work just fine and shut it off. Only to start it in the afternoon and the idle is back up to 1,600 RPM.
I've changed the IAC, TPS, MAP and all the vacuum lines. I ordered a smoke machine to do a through vacuum leak test which will be here in a few days.

I'm kinda leaning towards the PCM is bad but just a guess. What say you all?

 

I’d lean toward a vacuum leak that seals it self when hot. Possibly the intake manifold. Check for broken studs the hold intake/exhaust manifold to head.

Ron

 

I have the same problem currently have you made any progress ?