2003 Jeep Gr Cherokee - 4.7L Exploding Coils (FIXED we hope)

[jbadenoch]

have an 03 jeep gr Cherokee 4.7 sohc.

Vehicle came in running poorly and mil on. Codes were, po700, po320. Replaced ckp sensor. Upon start up eng was skipping on 3 cyl. Found 3 coils exploded. Replaced coils and started a single misfire on a 4th cyl. Found that coil exploded as well. Replaced that coil and all was fine for a couple days. Customer returned with mil on and stated was doing same thing, rpm gauge bouncing from 0-7000 rpm and eng would cut off. Checked codes first thing, po725, p0320, p1299, p1391. Vehicle was running well, no skips. Took for a ride and did not experience symptoms. Replaced ckp under warranty. Took for another ride and rpm jumped as described and vehicle cut off. Would not re-start for about 5 minutes and when it did start was skipping. Found 2 of the 4 coils we replaced had exploded. They are aftermarket coils and do not suspect it’s the coils themselves. Was reading a thread for a 02 dodge pu 5.9 titled "eating coils". That’s where I’m heading at this point. Any light to shine on this subject would be greatly appreciated. As a side note, the starter was fried when it came in the first time and we replaced.

Not thinking it is relevant but not wanting to overlook something.

[jbadenoch]

Just an update, battery voltage is 12.43, voltage at coils 12.43.

[liljoe]

Had an Intrepid with same problems, found wire harness rubbed causing coil to stay on all the time. Coil looked like the pic below...

BURNTCOIL OUT.jpg (163.6 KiB) Viewed 7046 times

BURNTCOIL1.jpg (95.89 KiB) Viewed 7046 times

[liljoe]

One thing to add, is that the coils did not puke the innards out till after the key was shut off and the current stopped. Never did make sence out of that part. My first thinking was a short to power with the key off, but testing found short to ground on the signal wire for that coil.

[brianp87]

Never seen this before

[liljoe]

I am curious if his exploded in the same manner.....

[jbadenoch]

Simular but not exact. Ours are melting and oozing out below the square top. Actually down in the plug tube. Chasing wires at this point. Not a lot of enthusiasm from the tech....

[liljoe]

Not a lot of enthusiasm from the tech....

For the life of me, I can not figure why not.....

[mopwrforme]

two things 1st there was a tsb for i think it was an 98 to 01 2,7 intrepid for burning up the coils the dwell was keeping the coils energized too long and would kill them also a 01 to 03 liberty w/3.7 liter intermitant cam sensor no code for the cam sensor we did find the coils burnt on it as well tech line explained it as the fuel equation was off on the dwell as well due to the false info from the cam sensor. basicly keeping the coils energized to long. thats all i got. there is a tsb for the 4.7 you have for a warm rouf idle which calls for a reprograming of the pcm thats all it gives me nothing on why just the symptom and the fix. i hope it helps let us know when you find a fix good luck

[jbadenoch]

Testing on this jeep shows a ckp count with eng off key on. Cmp not counting with key on. Anyone ever seen ckp counts without eng running. Going to head under dash to ign switch to do some testing per suggestion of steve k. Will try and keep you all posted. At least I won't need a hair cut for a while, lol

[jbadenoch]

Much more new info on this jeep. Replaced crank sensor with oem. We sent pcm out to california for testing and they called up a few days later saying pcm done and ok. I called them up and asked that they trst again only this time keep in mind the problem is intermittent and the vehicle can be driven for a few minutes or a few days before having an issue. They "re-tested" and said they ran the test for 30 minutes and pcm tested good. On a side note, I don't have a good taste in my mouth with this company because they tested a taurus pcm with no ac trigger and sent it back to me with a pass test on pcm. I spent a couple hours re-diagnosing and concluded bad pcm. Sent back pcm to them and this time found a problem and fixed. Sent back pcm and ac worked great. Back to Jeep. It will randomly cut off(when it does the tach bounces from 1000rpm to 8000 rpm and then stalls. Sometimes it starts right back up and sometimes takes a few minutes. When it starts up the mil is on with P0725 and P0320 (no signal from crank and no trans input rpm. The sense wire from the ckp goes to pcm and tcm only. The 5v ref is shared with tps, map etc. and the grnd is shared with other components as well. I ran new wire from ckp to pcm and tcm because the harness is difficult to get to behind eng and could not find any intermittent interupts in wires. Vehicle still does same thing. Does anyone have any insight as to the issue? I feel I'm second guessing myself for nothing because i feel the pcm is at fault. At this point, to summerize, good pcm,good wiring, good ckp sensor, nothing left, should be fixed. Bob in sc

[ricmorin]

Have you viewed the crank signal on a scope? That's where I'd be looking. Let's verify that the signal is there and stays good during a symptom.

[steven kiser]

a tach spike is usually cause by a signal loss. i would look long and hard for a wiring issue. i've seen a** on alarm or remote start systems cause issues because the connections aren't solid. it may not have one in it as far as the customer knows but a previously installed and then 1/2 assed removed one from a previous owner may be acting up.

[jbadenoch]

Just an up-date on this issue. We basically gave up on diag because I believe pcm is bad and I can't prove it. The company that tested it says it's good. We just sent it to Dodge and they are already saying possible pcm. They tell me on these jeeps that the only thing they have seen blow the coils is the drivers in pcm. I will keep all who are interested posted on the situation. By the way, I dug deep and no old or new alarm systems.

[jbadenoch]

Another up-date, dealer put a CAM sensor on it and told us to drive and see. It can take several days to act up so check back on thread if interested. Have a great day

[mopwrforme]

thanks for the feedback. and yes please let us know if it fixed it thanks again

[jbadenoch]

OK folks. We returned this to the customer mid week last week. Since we have not heard back from him I a** u me we are done with it. Now, would someone like to take a shot as to why this all happened? What did we miss in the dignostic process? Why would a failed cam sensor act like a bad crank sensor and why the heck would it blow out the coils?

[mopwrforme]

sorry for the late response. As per chrysler hot line, in the fuel trim equation part of the math used.
Is for dwell time, or the amount of time the colis are energized. if it gets a intermitant or false signal it can and will in some cases keep the coils energized too long causing them to burn up internally. my history with
this engine has been to the point you cannt trust what the pcm tells you I have many times sold.

both the cam and crank sensors with just a crank code due to the fact it will be right back in your face.
in a day or two with a now present cam code. but when you replace both you never see it again.

the logic for the 3.7 4.7 and 5.7 hemi is a bit off to say the least. You didnt miss anything, if you had
no access to chrysler dealer connect or there hotline you couldnt have know about this issue.
hell there isnt a tsb or recall on it. the only way i knew of it was fighting a 3.7 liberty for a day or two.

with burnt up coils after using there hotline and talking too the engeneres thats how i fixed mine.
then at that it took 2 days and several phone calls. you didnt miss any thing. im glad its fixed

[jbadenoch]

Thank you. I too am glad it is fixed. Nice to understand it. Looks like we will be replacing them in pairs from now on.