[Nanyo]

I recently bought a 2001 Jeep Cherokee Sport with 184k miles on it. It runs good, but the check engine light is on. I hooked up a cheap OBD-II scanner I got on Amazon and it says the cylinders are misfiring. I then took out the spark plugs and they're in terrible shape. I went ahead and looked around on this forum and everyone seems to recommend either the Champion Copper Truck Plugs or the NGK V-Power ZFR5N plugs. I went ahead and bought some NGK plugs. I am going to install these today and see how it goes. The old plugs gave the Jeep a rough start and rouge idle, and it seemed to suck down more gas than it should. Besides spark plugs, what are some other things I should look at that I could do maintenance wise? At 184k miles, I am sure something needs cleaning or replacing.

[biggn235]

Filters would be a good start.

[sbxj]

Congratulations on the XJ!
You're on the right track with the NGK's. The Champions are more of a lawn mower plug.
Pay attention to the condition of the old plugs and if you're new to Jeeps you should know that the 4.0 is not known for having a smooth idle and also misfire codes are not that uncommon even with new plugs. You might as well do the oil and filters, cooling system (sooner than later), tranny fluid and the diffs.
Have fun!

[CJ7-Tim]

1999 and older Jeep 4.0 L run best on basic Champion or NGK spark plugs. The distributor-less 4.0's run better on AutoLite Platinum APP-985.

The only filter that affects the running is the fuel filter, and it is not serviced unless fuel flow/volume testing indicates a problem.

Since you are unsure of the previous maintenance, you should change all the fluids. Some fuel injector cleaner in the gas tank might help.

[sbxj]

Originally Posted by CJ7-Tim

1999 and older Jeep 4.0 L run best on basic Champion or NGK spark plugs. The distributor-less 4.0's run better on AutoLite Platinum APP-985.

True about the distributor-less ignition and the real benefit is the longevity of the plugs @ ~100k

[CTron]

Might want to clean/test your injectors too...Leaking injectors can foul the plugs and cause a misfire that clears up after the fuel burns off...