'00 4.0l runs then dies. Need help.

Okay, this is my first ever post on this forum, and I apologize for it's length.

I'm dealing with the wife's 2000 Cherokee Sport 4.0l 4WD. Automatic.

One day she started it to defrost. It warmed up, and died. It started, drove 5 feet and died. Wouldn't restart. Starter cranks it over strong, but it doesn't fire.
That night I get home, start it, drive it into the garage, and it dies. Won't start. Next morning, it starts. Runs about 5 minutes, and dies. Won't restart. After it cools it will run a few minutes and then die. Suddenly shuts down, no sputter or hesitation, just like you turned off the key, except all other electrical systems continue running.
Mechanic says "coil or distributor" I agree that it's not getting spark since it won't fire even when spraying ether. Seems to build fuel pressure.
Replace with a new coil rail (distributorless ignition system). Same problem, no better, no worse.
Search internet. Subscribe to . Search....search....search. Learn how to retrieve engine codes from digital odometer. Displays "2.5" I'm assuming this means 25. Haynes manual says 25 is idle air control motor short or open condition.
Replace with new IAS motor.
Success! Runs and idles great. Runs over 10 minutes in garage.
Driving it to work the next morning, it dies, even after warming up for about 10 minutes.
Next morning it starts and drives about 4 blocks to our family friend/mechanic's shop.
He clears engine codes. Checks fuel pressure, good. Runs about 15 minutes then dies. It will start, then die within seconds, start, run a few minutes and die. He doesn't have complete diagnostic systems. He gives up on it.
I try again. Still displaying same "2.5" code on dash. Unplug IAS, runs at idle around 1100RPM for over 10 minutes. Dies. Starts, runs rough. Dies. Starts, run it at 2500RPM for a few minutes, dies even with my foot on accelerator. Starts, runs rough for 30 seconds and dies.
I'm stumped. I hate the dealership and I'd rather not give them any more of my money.
Where do I go from here? CPS? ECU?
Thanks.

I have a friend who had his start and run fine till it warmed up and changed from closed to open loop (or vice versa), he put $1000 into parts and took it to 3 shops (including dealer) and none could figure it out. Posts on here led us to figure out it was the CPS sensor. (Buy this part from dealer - Autozone, etc sell the wrong ones for a lot of models)

I didn't search much on the CPS because I had the IAS engine code. Searcing in the forums returns several CPS problem posts that seem to be much like my own.
If I replace it (CPS), do I have to clear the trouble codes?

The Haynes manual says not to try to clear the codes by disconnecting the battery......oops. How should I do that? I don't have the proper scanner and my wife is fiercly opposed to me spending $150 on one. She'd rather pay the stealership $300 I guess. I'd let Autozone do it but it won't drive that far.