Jeep caught fire and now misfire.

95Trooper

Well-Known Member
Joined
Mar 23, 2008
Location
WNC
I had a guy at my work do a state inspection on my 1996 Jeep Grand Cherokee with a 4.0 yesterday. He suggested a oil change because the last person that changed it put the oil filter on so tight that it was causing the seal to leak. Changed the oil and filter and everything was fine. He sprayed brake cleaner on the passenger side of the block because there was grease/oil build up from a previous valve cover gasket leak. He waited about 5 minutes and cranked it and it caught fire right where the coil is but it was just the wire loom coming from the coil. We checked all the wires inside the loom and they appear to be fine. He put the fire out in enough time before it got bad.

I didn't notice it until I was driving the Jeep home though that the Jeep was missing. At idle it will be idling smooth and then just out of nowhere jerk/stumble. You can't feel a miss while driving it down the road. It's just at idle. Also, when sitting at idle and revving to slowly build up RPM's it will start hesitating/cutting out/missing at 1500-2000rpm's if you just let the RPM's gradually build. If you stab the throttle it's fine though. The Jeep didn't miss a lick before I brought it into the shop. Is the Jeep going to need a wiring harness or??
 
what did you use to put out the fire ?
 
i dont think i would miss the fire that caught my truck on fire :confused: maybe thats another jeep thing

-haha other then that, i cant be of much help
 
Most likely a plug wire was arcing (sp?) And started the fire. Been there done that. Might try a test light hooked to ground and run it up and down each plug wire looking for a arc!

Sent from my DROID RAZR using Tapatalk 2
 
I replaced the plugs and wires that evening thinking that was maybe the issue. Champion 412's and Bosch wires. The spark plugs and wires in the Jeep didn't look like they have EVER been changed. What else could be wrong because the Jeep is still not running right? Also, when I pulled the old plugs out they had white haze on them and every single one of them were gapped at 0.060...I gapped all my new ones to 0.035
 
Did a compression test today. #1 cylinder showed 165psi where as all the others showed 185psi. I doubt this is my problem at all. But like I said in my previous post..every single spark plug was gapped at .060 evenly. I thought to myself that maybe it's just because they're worn but is it not weird that they were all at 0.060? Should I try upping the gap on the plugs to see if it runs better? I know it calls for 0.035 gap but I'm just trying to get this figured out. Thanks!
 
Last edited:
95Trooper said:
Did a compression test today. #1 cylinder showed 165psi where as all the others showed 185psi. I doubt this is my problem at all. But like I said in my previous post..every single spark plug was gapped at .060 evenly. I thought to myself that maybe it's just because they're worn but is it not weird that they were all at 0.060? Should I try upping the gap on the plugs to see if it runs better? I know it calls for 0.035 gap but I'm just trying to get this figured out. Thanks!
Click to expand...
You could look at fuel trim to determine the type of misfire. You could use an oscilliscope to verify the ckp and cmp waveforms look correct. You could also use a dvom to check power and ground at the ckp, cmp and coil. Its up in the air without more information which direction to go. Is it possible its a coincidence it occured after the fire and not directly related? The plug gap is likely a result of the age of the plug. Might be worth while to relearn adaptives and drive it a while. Might also be useful to check fuel pressure. Some of the chrysler products used a two peice pcm cover which utilized two screws directly under the pcm connectors. These screws would eventually rub through into the circuitry and short the computer to ground. However they symptoms are not even close to being the same, with the pcm issue you would get a coil primary code and a stall with backfire.

Sent from my SCH-I605 using Tapatalk 2
 
mysterync said:
You could look at fuel trim to determine the type of misfire. You could use an oscilliscope to verify the ckp and cmp waveforms look correct. You could also use a dvom to check power and ground at the ckp, cmp and coil. Its up in the air without more information which direction to go. Is it possible its a coincidence it occured after the fire and not directly related? The plug gap is likely a result of the age of the plug. Might be worth while to relearn adaptives and drive it a while. Might also be useful to check fuel pressure. Some of the chrysler products used a two peice pcm cover which utilized two screws directly under the pcm connectors. These screws would eventually rub through into the circuitry and short the computer to ground. However they symptoms are not even close to being the same, with the pcm issue you would get a coil primary code and a stall with backfire.

Sent from my SCH-I605 using Tapatalk 2
Click to expand...

I drove the Jeep some last night and this morning. It did much better last night than it did this morning on my way to work. While driving up hill this morning right around 1500rpm's you could tell it wasn't right. Rather than the RPM's gradually increasing the tach was slowing jumping up just like it does when I rev it up at idle. It did the same when getting on the interstate and the converter locked up. The tach would start jumping slowly from 1500 to 1700 then to 2000rpm's rather than smoothly increasing but would then clear up and drive fine after 2000rpm's. It wasn't doing anything of this last night on my way home from work. Fuel pressure is at 50psi so right around where it should be. I had it checked here at work yesterday.
 
Id swap the TPS with a known good one...they can cause all sorts of problems from what Ive heard.
 
Back
Top