I have this issue about every other day. It will happen if i drive about 5 min in the am from a cold start to the corner store and stop, leaving it running it will start loping like it has a cam or something. No codes either. It will stumble and start doing this. Cleaned maf and iac no difference. Running down highway no problems.

 

It's a real pita, but you might try replacing the old plenum bolts that attach the bottom half of the plenum (the black composite plastic piece made up of two pieces. Top half and bottom half) to the top of the intake manifold. The newer design uses a softer rubberized material that will not let air bypass (get sucked into the intake) the throttle body. The old bolts were a design flaw and a lot of 4.2 v6 motors expirience this. This caused my engine to idle very badly to where it would stall while in park, and lunge by trying to keep running when at a stop light. If that makes any sense to you. Cost about $40 for the set. You'll need a deep well 8mm socket to reach the back bolts of the top half of the plenum. That's the pita part of the job. The rest is a breeze. You might as well replace the plenum gaskets while your in there. Add another $45 for that. Hope this helps.

 

Yes sir i had that on my mind as the issue. Not too bad of a job. I can do the work myself