97 grand cherokee rough idle, spitting, sputtering, misfiring

Ok, I inherited this suv from my mother about a month ago with 172000 miles. Its a 4.0. Its is in excellent condition. However my parents have had none stop problems with the motor/electrical problems. The thing starts rough, it idles like it has a 500 big block in it, and it skips like hell going down the road. I have replaced the rotor cap, plugs, wires, checked ground wires and have also replaced the pcm. No help. However I think I finally have found the problem. Tonight I was tinkering with it in the dark and fired it up. When I did I noticed electrical sparks around where the distributor cap is. Now can anybody help me troubleshoot this issue? Would this make the jeep run this rough, considering I replaced the cap and plug wires and its steal losing spark? As well is there any other troubleshooting ideas before I just take this thing to the dump. Thanks

IIRC there should be a screw to hold down the distributor cap; if that's not tightened and/or is missing that could cause your issue.

Also, you said "rotor cap" was replaced....was this the rotor, the cap or both replaced?