My 89 Montero SWB automatic trans, Cranks quickly and revs cold at 1800 or so and idles down as it should when temp gauge comes up. When you first drop it in gear from high idle it bumbles for almost 1 second with the engine speed dropping to around 800 for that second then idles up to about 1k rpm smoothing out. It will stumble again just enough for the nose to drop a tad if just a tad of throttle opening, then smooths up. Feels just like a carb with an off idle flat spot would feel.
More throttle = more go with no misfiring cold or hot just as it should. Transmission shifts just as it should both cold or at running temp.

I pulled the cap and plugwires last night which looked ok, plugs looked alright as well. Not quite tan but not bleach white and no soot at all. No funny arcing under hood in the dark, nor did misting water on the wiring change anything. It seemed to have a little more stumble after all that so I ordered wires/cap/rotor/plugs/fuelfilter just because it hasnt had any tuneup parts since i had it.

Question is if the new parts list doesn't resolve this, is the stumble a telltale of a bad sensor, temp or tps?

Thanks for feedback on this guys, im sure im not the first with a stumble like this.
Mike

Remove the ICM and thoroughly clean the throttle body, especially the seat and plug of the ICM. Check for intake hose leaks especially in the accordion hose. It hasn't been cold enough here in Jawjah to be causeing this.

Mine does the same thing in appx 60 deg or colder temps. Clears up after the first 30 seconds. I just ignore it. I've had the issue for years and notice no real problems it's causing.