I put a 98 4.0 engine in my 02 Cherokee Sport, the 02 utilized a coil pack ignition system and the 98 utilizes a distributor style ignition. It will start but i am not getting spark to all cylinders. Do i need to chang the PCM? If I do need to change the computer does it have to be from a 98, or will other year PCM work?
Thank you

 

You need to swap the coil pack ignition system onto your engine, and 01 was the last year of the Cherokee.

 

Depends on which ignition system you are using. And 01 was the last year for the Cherokee XJ.

 

So you have a number of problems I believe. I may be wrong, this is off the top of my head.

First, you have an out 02 that means your wiring system and ECU is designed for the COP "coil on pack" system.
With an engine from 98 that utilizes the DIS "distributor ignition system".

In order to make that fit you're gonna have to swap your old head back on. Or figure out how to rig the coil pack firmly in place.

Next problem I believe is going to involve the CPS (camshaft position sensor). The 98 block may not have the same bolt pattern to accommodate just the CPS. Since the 98 block was made to accommodate the DIS. On the 98 block the CPS was inside the distributor.

Besides those two issues I've mentioned. Everything else should be as original as the old block.

 

Only in the USA. Outside this country the KJ was called Cherokee. It's only called a Liberty here.

Regardless, the XJ and KJ are completely different Jeeps with different engines that are not compatible. I wonder how the OP got an XJ engine to fit in a KJ.