Alright boys here's my problem, When i start my jeep fires up great runs fine for about an hour. After about an hour or so it starts running like it's got a bad vac leak and when you hit the gas fast a few time"Kinda like tapping it fast about five time" then you lift of the gas it will high idle like 3 grand then u drive it a sec more it will try to die. Im not sure what its problem is the cel will also come on but if you turn it off the light will go off and it will run fine for about 10 mins longer then same problem comes back. i have looked on here but cant find anything at all so please help and thank you...... "It has no lose of power and is not over heating or anything"

 

Idle Air Control maybe. I know they can stick sometimes. Look at threads dealing with iac testing and cleaning. Check out you tube on this also.

 

The strategy for a check engine light is always the same. Pull the codes! The fact that you have symptoms and codes is not a coincidence.
Use the technology provided to you by your Jeep. Anything other than this is pure guesswork. You have had a check engine light so you will have "stored" codes, even if the check engine light isn't currently on.

Below is the procedure for pulling the codes on your 91. Post back what code(s) you have for additional guidance.

Retrieving OBD codes on the Jeep Cherokee (XJ) OBD1 Models: 1991-1995

1) Start engine (if possible). Move transmission shift lever
through all positions, ending in Park. Turn A/C switch on and then off
(if equipped).
2) Turn engine off. Without starting engine again, turn
ignition on, off, on, off and on within 5 seconds. Record 2-digit
fault codes as displayed by flashing MIL.
3) For example, fault code 23 is displayed as flash, flash,
4-second pause, flash, flash, flash. After a slightly longer pause,
other codes stored are displayed in numerical order. When MIL begins
to flash fault codes, it cannot be stopped. Start over if count is
lost.

NOTE: A "5-5" will always occur to signal the end of the sequence. Some will flash the "1-2" code indicating a recent battery disconnect even if you haven't done it. Ignore these two codes, and mark down all others.

 

Runs like crap after an hour is not much to go on, have you checked the blinker fluid?