Interesting Idle Issue

99, 4.0, AW-4, 87,400K.

Here's what happens:

I get, engine is cold (sitting over night, or if it's really cold outside and it the engine sits for a few hours). I fire it up, everything is running great. Driving down the road, stopping at various stop signs and traffic lights, engine isn't warmed up all the way yet. While i'm still driving down the road the engine finally hits 210 and still all is well. The first time I come to a complete stop after the engine has hit 210, it will begin to idle just low enough that you can feel it. The tach drops to about 500rpm or so. This only lasts for about 1, maybe 2 seconds. I can also give it a little bit of gas while this is happening and the idle will straighten back out, and all is well for the rest of the day.

Now that it is winter and the temps are getting colder i'm noticing it more and more.

I've been chasing a o2 sensor #2 high voltage issue for a while, and i'm about to replace that sensor, but I doubt that has anything to do with this.

I searched around on here and didn't really find anything related to what i was looking for.

Does anybody have any ideas as to what might be causing this?

Now that i'm in school, the Jeep sits outside for the majority of the week and doesn't get driven. Friday mornings when I go grab some breakfast, it seems to do it even worse that very first time (probably from sitting all week), but I drive 90 miles home every Friday and 90 miles back to school every Sunday, all highway travel.

Idle issues for me have always been from a failing Throttle Position Sensor. The TPS system is also known for developing a poor ground, worth checking both ground and connector before replacing the TPS. The problem arising when the ngine gets warm is a give-away: resistance changes with temp enough to through things off. I'm betting it is the sensor itself, especially if you start to notice a bit of weirdness in the tranny shift timing.

Last spring right as I started having o2 sensor issues I was driving down the highway and the Jeep started coming out of gear, and not staying in any particular one. I pulled over shut it down and re-started it and all was well. It threw a code for the TPS, but it's never done it since.

Except for that one strange incident, the tranny has always shifted normally. I'll definitely check the grounds, I didn't even think to check there.