2001 low idle issues

I've been having some low idle issues in my '01 XJ. They have struck before but have seemed to become more consistent in the last week.

The vehicle started dropping RPM when you put it in Gear (AW4). Lately it has progressed to low idle since start up. You have to lay on the gas to get it to start then once it gets rolling it struggles along about 400 rpm. What I don't understand is some days it gets better after warming up, and some days it starts and idles fine initially, then once warmed up it starts idling low. No Check Engine Lights and it runs fine above 1000 rpm.

When they first started happening I changed the rear CCV and it solved the problem for a few weeks before I noticed it again.

The spark plugs are a year old, good gap (champion OEM). I cleaned the throttle body, have checked Vacuum lines, replaced both CCV elbows. I did buy a second CCV for the rear that is unrestricted (identical to the front). With the unrestricted CCV in it idles fine and within normal ranges. I am clueless, especially since it doesn't have a CEL. Another factor that may be minimal is I recently moved. I gained 1000 ft at my home, but work is 2000 feet lower than previous home location.

Can someone possibly clue me in before it goes to the stealership?

Also to note, Jeep has 131,000 Give or take a few hundred. Mostly original powerplant. AEM intake, Gibson exhaust.

The fact that you have to tip in the throttle to start it might be a clue.

I've seen XJs with that symptom that have a bad throttle position sensor. They can be tested with a meter (analog best) and a manual with the procedure.

Did you clean the idle air control when you cleaned the throttle body? Always a good idea as they get as carboned up as the throttle body does over time and miles.

Good luck!

Intake leaks will lean out the mixture and raise the idle speed, although the PCM will attempt to correct the condition by lengthening the injector pulse duration to richen the mixture.

A rich condition will lower the idle speed, although once again the PCM will attempt to correct the condition by shortening the injector pulse duration to lean the mixture.

Things that cause a rich mixture--an exhaust leak upstream of the o2 sensors will cause the o2 sensor to report a lean condition to the PCM; bad MAP, bad MAT, bad CTS, bad thermostat (engine too cold).

I did clean the IAC when I took the Throttle off.

Does anyone have the sensor test limits for the TPS? My Book only has them posted for 1997 models and older.

Replaced the IAC, fixed the issue. Thanks for the help.