1995 Jeep Cherokee ruff running

i have this problem, i really cant figure it out, hopefully u might point me in the right direction, the jeep starts, it runs for 10 - 15 minutes smooth, then it get s real ruff idle for 3 minutes, then the jeep will run smooth again for 10 -15 minutes and it does it again, i have replaced the fuel filter, i replaced the cps on the transmission bell housing, i tried a ccoil but it didnt make a difference, any help would be appricated