I just found something that has driven me crazy for a while. 96' 4.0l xj
Symtoms: Intermittent hard start. Intermittent runs rough at start only; smooths out rusn great. Drove 50-70 miles ran perfect. Next day sometimes hard start. other times perfect. Finally would partially hit barely run couldn't keep running. Looked on other posts. replaced CKS, good spark, good fuel pressure, wouldn't run off of ether. I finally checked compression found no comp. on cyl #1,2,5,6. checked found all but #3 intake pushrods bent. replaced pushrods, now starting but rebent #6 and found #5 valve stuck down. I guess varnish on the intake valves. Is this a common problem on these 4.0L engines?

P.S. brother in-law overheated and it sat dead for years before I got it.

Hope this helps someone else.