[99_wj_QD]

so the information i recieved is as follows: cylinder #2 is misfiring thus causing a change in crankshaft speed. possible causes are a bad spark plug or coil, a vaccum leak, an injector fault, or high/low fuel pressure.

also, my exhaust has a hole or a leak of some sorts around the cat that is in the middle of the chassis. it is creating a very loud and deep grumble and releasing a "hot, burned odor". so i am thinking this is a catalyc converter issue, im pretty good with cars and can install or perform almost any maintenance myself. i hate taking my cars to mechanics because i feel i constantly was overpaying for sub par service.

any help from other WJ owners who have dealt with this issue and dealt with it successfully would be greatly appreciated in finding the cause of the misfire code. then from there i know how to fix all the possible issues, mainly i just dont want to waste money replacing parts that do not need replacing.

note: just changed out the spark plugs to bosch platinum +4 plugs and gave her the first synthetic oil change. was running amazing until about 350 miles after the tune up. thats when the cat seemed to start leaking and the engine light came on and when im idling the motor has a slight constant rocking to it as if it is unbalanced and there is intermittent flutters of 100rpms during idle

[99_wj_QD]

*and the plastic casing of the ignition coil for that cylinder has a crack around the plastic right on top of the rubber boot

[kodiakwj]

First off what motor- 4.0 or 4.7? I know that my 4.0 hated those plugs and ran like garbage about 1000 miles after I put them in. Put stock ones in it ran fine. In your second post you said the boot on the coil rack is cracked, I would bet that plug is arcing through the boot. I also had this code pop up again and the injector was bad, replaced and still runs like a top. Hope it helps.

[99_wj_QD]

thanks kodiak, its a 4.7 by the way, i ended up doing some more research and then came up with the idea that should of hit me when the problem originated. i simply put the coil from cylinder 1 onto cylinder 2 then reset the codes. 20 minutes later a code popped up for cylinder 1 misfire. this allowed me to pinpoint that it was indeed the coil that was bad and NOT my injector or plugs or vaccum leak or fuel pressure.

hopefully anyone else with this similar problem in the future can search the forum and come across this because when i searched the forum for my problem i did not find anything of much help...mainly users trolling about what spark plugs they think are "best"

[Rocklobster]

I'm glad that worked out for you I am still chasing a random misfire in my 2000.The best plugs in both engines are the stock copper champion plugs by far. Just my .02