Idle Problem - 1995 4.0L

Hello. My '95 4.0L recently developed an erratic idle when warm and cold. Using my Haynes Manual and a multi-meter, I tested all of the sensors and discovered a faulty O2. All other sensors tested ok. I also cleaned the IAC and throttle body. The problem was solved after installing the new O2.

Now I'm having a new problem. Upon cold starting, the idle is perfect and it runs great while in Park. However, as soon as I shift into gear, the engine stumbles for a few seconds. It doesn't quite stall and runs fine at higher RPMs. It only happens during cold startup and runs great otherwise. There is no "check engine" light and no trouble codes. WTF? Any thoughts or ideas? Thanks.

OlyJeep

Hard to say. Last time you had a tune up? Maybe its the TPS? Sounds like something to do with the fuel. IMO

Full tune-up has been done recently...new plugs, wires, cap, rotor, fuel filter, air filter, etc. I've checked the ground connections and other electrical connections, no vacuum leaks, intake manifold bolts are tight, no blown fuses, etc, etc, ect. It's a mystery. Luckily, it fixes itself after warming up and runs great otherwise, so it's not a major issue. It just pisses me off because I'm a perfectionist.

When you did your o2 did you remove your cables to re-boot your computer? If not you could try that to see if it helps

Yes, the battery was disconnected prior to installing the O2.

Definitely test your throttle position sensor.

Pretty easy to do with a meter. Sometimes you can have a marginally flaky TPS and it won't set a code.