My Jeep Cherokee has the 4 cylinder, 2.5L engine. From the day I got it I felt it ran just slightly rough. I took it in under warranty and they said there was nothing wrong with it, but that's not surprising. It's just a mild, partial miss, under load, at low to medium RPM's.

So now I have 133,000 miles on it and have had to replace the engine. Lost a connecting rod. At any rate, it still has the same "feel" to it. I've tuned it up repeatedly and replace the wires with different styles, qualities and brands. I am considering going back to the dealership and getting the tune up parts from them. My gas mileage is getting progressively worse.

My gut tells me it's the ignition. There seem to be reasonably priced replacement coils which have a bit more spark. This would both check and replace the existing coil, which must be suspect. Are there other ignition components (non tuneup) which could be suspect?

Any thoughts on "beefing" up the ignition system. I don't want to spend hundreds of dollars on this. However, buying quality replacement parts or moderately priced performance enhancements are certainly wise investments.

For that matter I guess it could be air inflow or even injectors but I lean toward ignition. Any thoughts, experience or suggestions would be greatly appreciated.

Have some one run a computer diagnostic,take it to AutoZone they can run a code check on it and see if it will kick up any codes.
Guessing can be expensive in that once you put an electrical part on and still have the problem....it can't be returned.....unless the part itself failed..

First, how are the spark plugs. IMO and other Jeep techs, Champions are the only plug that "lasts" in the 4.0L and yours I know is the 2.5L, but it might make a difference.

Then, maybe check the map sensor.

some instructions for that:
http://www.dua1.com/AdminFiles/Jeep/00/00_XJ_Map_Sensr.pdf

From what I've read on the forums I frquent....the 2.5 is not exactly an engine that ANYBODY has anything good to say about...IT JUST AIN"T GOT NO BALLZ.....

Don't know what happened to GK..he never wrote back....