Jeep stumbling

My 91 Jeep cherokee with 150000 miles started stumbling the other day. I changed the plugs, cap and wires and stuff look fine. It seems like it is missing it kinda surges when I am driving steady. Any ideas what this might be? Sensors, what? Oxygen sensor is pretty new. Cat is not clogged. New Muffler, Borla header, no exhaust leaks. Vaccum system seems like there are no leaks. What else should I check?

Thanks.
MIke M., New Mexico

I had the same problem on my 88 xj. Missing surging stalling. Unpluging and repluging sencors and many Changed parts, nothing seamed to solve the problem for very long. Than I took of the throltle body and cleaned it real well with carb cleaner. After almost 2 months now I have no stumbling or hesitation. Good luck, I know how frustrating the problem can be.

Fuel Filter, Fuel Pump

I recently had a stumble,hesitation,kinda cutting out when I hit 3rd or 4th on a 90' w/aw4,did it really bad climbing hills.Checked lots of parts but in the end injectors were the problem.I just cleaned them up and put new o rings on.Previous owner had let the "blow by" problem go for a long time resulting in oil residue throughout the air intake system eventualy coating injector tips among other things.

Easiest way to check if injectors are problem is to disconnect signal wire one at a time and take notice of any change in motor speed.Injector not functioning right will not cause any change in motor speed.Give it try easy enough to rule out.

Jeep 91, if you have not replaced the CPS at 150,000 it would be time and money well spent to do so. I had symptoms similar to what you describe and it turned out to be the dreaded CPS. Good Luck !!!

If you have an EGR valve, try diconnecting the vaccuum and plugging the line to see if it helps. It may be sticking and need cleaning or replacement, or the solenoid that controls the vaccuum to it may be bad (like mine was)
HTH,
Jeff