i have a 97 cherokee 4.0 and for the past like 6 months every once and awhile, almost every other day a couple times. itll idle really low and then idle rough, around 20 to 30 mph it sounds like its either starving for gas or misfiring. idk witch one though. less power and pickup it seems like. nobody can figure out wat it is. and i pretty much gave up on what it could be. if i get on it pretty good it doesnt happen but we i start real slow(drive like an old lady) thats wen it seems like it happens more.

 

any engine light? does this mainly happen when you restart it when hot?

 

Does your battery voltage drop when it starts to run rough?

 

But i say, might as well do plugs, wires, cap and rotor.
I bought my XJ cheap from an old man who said it had "tranny problems with problems shifting"
It just needed those things right there. if you havent replaced them in awhile, or at all, i would say start there

 

prell. yes the check engine light has been on for awhile now.. the codes that pop up are the up stream o2 sensor. i put after market nes in then switched back to factory and that code still pops up. i havnt noticed any change in the voltage. and ive done a tune up, new map sensor, new exhaust, upgraded the pcm, and still the same thing. it does it at random times. its never consistant. but say it does do it after i restart after hot. wat do u think it is?

 

Check the O2 fuse I the engine bay. I replaced almost every sensor and checked the fuse last. Could've saved some coon

 

Definitely sounds like the fuse to me. IIRC it is the middle fuse closest to the relays.

 

Knowing the CEL code I would agree with the previous two posters

 

alright thanks. ill check it tmrw