I can't tell you what the problem is, but perhaps your on-board diagnostics can. I think cherokees through 1997 have the on board diagnostics - if something is wrong with your engine or emissions, the OBD will most likely let you know. Put your key in the ignition and turn it (but don't start the engine) to ON, OFF, ON, OFF, and then turn it to ON and leave it. You have to do this sequence in under around 3 seconds. If your powertrain control module has any trouble codes stored, the check engine light will flash. The codes are two digits. Example: a trouble code 35 would be 3 flashes, a pause then 5 flashes. (more than 1 code will be separated by a long pause)
If you try this and get trouble codes I'm sure that if you post them, someone here can let you know what they mean. I hope this helps ya.