Weird Hesitation

Okay here is a good one. I just bought a 98XJ last week. It is the 4.0 automatic. 106,000 miles. It runs great except that every once in a while (every other day?) I will get a strange power loss sometime between 30-90 seconds after starting to drive down the road. Power and engine speed will drop and if I give it more gas I get strange sounds from underneath the XJ but no power gain. If I let off the gas a little and get back in it everything is fine. Usually letting off once solves it for a day or so, sometimes it takes twice. It is almost like something is resetting when I let off the gas. Is there an autozero feature in the ecm for the TPS? I know our diesel engines use that on the electronic throttle pedals.

I am pretty sure if I let the engine idle for 30 seconds or so before driving I never get the problem. I am suspecting it is a spark or fuel delivery problem. I just do not know if it is mechanical in nature or electronic. The fact that it only happens once and only after starting the engine makes me think electronic. What does the engine use the TPS for besides the tranny?

wild shot in the dark here, but could be the IAS. at over 100k on the odometer, i bet the throttle body is all gunked up. use air intake cleaner, NOT carb cleaner. if you do a little searching about the use of seafoam, you could try that as well.
ive got a 2000 with 66k on it. its only ever done that once.

Is it doing anything listed in this thread?

http://www.naxja.org/forum/showthread.php?t=71220

It sounds just like the description in that thread only if I let off the gas completely for a second I am good to go with no popping or any awful noises. It seems to be happening less frequently now though. I wonder if the Jeep sat for a few months and now that I am driving it everyday whatever gunk was causing the issue is wearing off?

Would that IAS affect the engine when not at idle?

My 99 XJ with 64K does the exact same thing. I noticed if it is really cold or I just start and drive without a small warm-up it will hesitate. I am in Iceland and the only fuel to run in 95 so I doubt it is that. I just replaced the plugs and wires. I just try not to be in a hurry. Seven years old it is bound to start acting weird sooner or later.

Will
99 XJ 4.0 AW4/231 D30/8.25 3.5" 31's and bigger plans

Well I cleaned the TB last night and no effect on the problem. Should I be getting a check engine light if it is an oxygen sensor problem? I did find out that engine temp has nothing to do with it. I parked the XJ for 30 minutes and then went somewhere else in it and the problem repeated despite the fact that the engine coolant was still around 200. It almost seems like a few good seconds of engine braking fixes it until the next time I drive it.

Are there ever any fault codes that do not light the check engine lamp?