EZEARL

For a good while now if I would start up(fast idle working),drive a couple miles,stop,and put trans in park the motor would either crap out but mostly the idle would drop to a lope. If it crapped out it would start up and be at normal operating temp idle. If it would lope I could just hit the throttle and get the right idle. Just the past couple days I've lost the fast idle. Starts and idles like at operating temp. Also the crap out and loping have stopped. Been meaning to pull the TB and IAC for a cleaning. Sound like an IAC issue?

Gee oh Dee

Sounds like it. Check codes? They may have tripped but not thrown the CEL.

EZEARL

I'd planned on it but the CEL is on now. Today I pulled my serpentine belt,checked/cleaned it,and checked/cleaned pulleys. Forgot I had unpluggled a connector and bumped the starter to center the belt before plugging it back up causing the CEL to come on. It'll go off with a bit of driving. Picking up a TB gasket tomorrow.

EZEARL

Cleaned the TB,IAC,and replaced the TB gasket. Went from 650 rpms to 1050 which is the new cold or warm engine idle rpm. 650 use to be my operating temp rpm and 1050 or so was my cold engine start up rpm. One thing is different now and this is with or without the IAC plugged up. When the engine is started it's at 900 rpms but within maybe 30 seconds it goes up to 1050 and stays. Vacuum readings are a steady 17mmHg at 900 and 20 at 1050.
CEL(which hasn't come on since my problem started)went out(my fault it came on)so I checked codes and came up with two. (Haynes)12 and 22. I can't tell you the last time the battery was disconnected(12) and the temp gauge seems to be working fine(22).
I'm still reading up to test for other possible causes but was wondering if what I've got so far rings any bells with someone.

Gee oh Dee

I'm better with p codes than the 2 digit numerical codes. :/

freegdr

http://jeep-xj.info/HowtoECUcodes.htm

EZEARL

12- battery disconnected (batt voltage to PCM disconnected within last 50 key-on cycles).
22- coolant temperature sensor or circuit (check coolant temp sensor circuit. check sensor resistance. replace sensor).

CEL showing code 25 (IAC circuit) now but I had it disconnected.