Update: So the TSB about hot start misfiring refers to heat soak on the #3 fuel injector and recommends the installation of a little shield.
I ordered the part from a Chrysler dealership and installed it (no tools required), but until yesterday had not had a good opportunity to get the engine hot, run the A/C for long, and on a hot day to boot.
So yesterday, drove an hour and a half at 75mph, A/C cranked, pulled off to a gas station.. when I got back in, crossed my fingers. No misfire! That $6 part really works. It would misfire after even 10 minutes on the highway with the A/C, after sitting for a few minutes.
So, if you've got the 4.0 and you notice a miss (mine was BAD) when you restart after the engine is hot, then check out the TSB:http://www.wjjeeps.com/tsb/tsb_wj_1803103.pdf
And get the shield, install, and be happy. It really does work, I'm amazed.
Seems like it only happens after I've been running the A/C, then parked, and restarted before it's had time to cool down much.
I always start the engine with ALL accessories turned off, for what it's worth.
The needle will be just above 210 from sitting, and I start it, and it misfires... BAD... for about 5 seconds until it smooths out, then it's completely normal. Behaves perfectly under driving, etc. Only really seems to happen after I've worked the A/C for a while.
Oil and coolant look good, changing spark plugs would be next.. but why could this be happening?