It's the crank sensor!
Join Date: Nov 2007
Location: Central Minnesota
Do research on CRACKED 0331 CYLINDER HEAD + JEEP CHEROKEE On all XJ forums and also just using a simple Google search. There are literally hundreds of threads on it, so no need to reinvent the wheel here.
I'm not saying that is your issue, but it sure could be and as an owner of a 2001 XJ, it's imperative that you understand it.
Good luck and keep us updated!
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!