Weird problem

Hey guys
I have a problem with my 91 limited ( 141k) I will drive it for a while and when it is hot the engine will shut off. Most of the time with a little enthusiasm it will start but sometimes it won't and i will come back in an hour or so and it will start and run just fine. A couple of people in here told me crankshaft position sensor so i tried that and it seemed to help for a while but it started to do it again here lately. Now last night I had it happen again and now it won't start. After doing some investigating there is no spark.
hope that helps and hope you guys can help me.
Thanks
CUJeeper

JUst a guess. Back in the early 70's I had a 63 Ford Falcon that used to do that. I replaced the coil based on a mechanic's advise and it fixed it. Seems that a break in the interior wiring of a coil will separate when heated up.

However, based on my experience with my TPSs I'd change that out and see if it helps. They seem to be affected by excess heat and then will get progressively worse until almost any heat will cause them to act up. Keep in mind that a fault in one part of a vehicle system often leads to more faults down the electrical or mechanical chain. Especially in the newer vehicles.

If you're comfortable with the grounds, fuses, and fusible links (never hurts to check)...
... faltering on hot is consistant with a CPS failure (look at it's resistance, if you crank the engine while watching it's connector with a volt meter or scope you should see some AC voltage), Dist-Sync output or an ignition coil.

The no-spark is also consistant with a failed CPS or ignition coil -- If you have a factory tach you should be able to determine this quickly -- if, while you crank, the tach moves, that indicates that the computer is seeing signal from the CPS. If your tach does wiggle (representing your crank speed) then look to the secondary stuff (igniton)

I seem to recall, perhaps from a post by Rags, that the coils on the early Chrysler 4.0's (i.e 91-2) are pretty notorious for failing, and a failure when hot would be consistent, as CUJeeper notes. I had mysterious problems on a 93 with a splice in the wiring harness that failed only when hot, but this just messed up the injection, didn't kill it outright. Still, if nothing else seems to work, you might have to go at the harness with an ohmmeter when it's hot and see if something is changing. Finally, you should also check the "automatic shutdown relay," in the relay cluster, because that, I believe, controls the positive side of both ignition and injection (on the Chrysler system, the hot side is always on with ignition on, and the ECU switches the ground side). I can't recall whether that relay is interchangeable with others, but if it is, one way to check would simply be to swap it with a less-important one, such as the a/c clutch relay.