Okay... I bought a 1996 Cherokee sport yesterday. I took her through emissions testing today and she did not pass. The emissions testing center did not take a reading at the tailpipe. Instead, they read an error code on the vehicles diagnostic port. The code was for random misfires on cylinders 3 and 4. My question is what is the most common cause of this? I'm going to be on a pretty small budget for a little while and would like to take care of this myself if I can. Just curious if this was common enough that some of you guys know where I should start looking first. Any help or suggestions would be appreciated! I had so hoped for my first post to not be a technical issue. Oh well, I guess you gotta ask for help some time! Thanks!

 

Incorrect plugs or cheap plug wires. 4.0's love Champion plugs use the ones listed on the emissions tag under the hood.... RC12YC I think. Check the #3 and #4 spark plugs if the white porcelin has black marks running down them that is your mis-fire. I run all Mopar parts on my Xj and never have a problem.

 

Wow... That did it! (I think). Replaced cap, rotor, wires and plugs. The previous owner had a disturbingly wide variety of plug gaps on the plugs. Also the wires were getting a little old. I took the time to replace them and rout them in the factory wire clips properly. Disconnected the battery to erase the error codes and immediately drove her for about forty miles both in city and on the freeway. Check engine light has yet to come back on and she starts and runs better and smoother. I had a feeling I was dealing with something ignition related but it was nice to consult with you guys to be sure I was on the right track. All in all it was a minor issue but thanks for being here so I did not have to go it alone!