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Unread 08-22-2011, 10:32 AM   #1
mnilsen
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Ignition Coil failure, two in one year, out of spec on resistance

1999 TJ stock 6 cyclinder

OK, I have had two unique failures of my stock ignition coil. The first one was about a year ago and after going through the troubleshooting in the shop manuals, I got to the coil and the resistance was 10500 ohms on the coil, which is out of spec (normal I believe is 11500 to 15500). Replaced the coil, happy Jeep. Relieved owner.

1 year later, same kind of failure (Luckily this time NOT on the trail). Same process, same results (around 10500 on the pulled coil), replaced the coil. Jeep happy again. Owner not so.

Here is the kicker...when I bought the coil the second time around, I checked the resistance at the parts store and found the coil they were selling me was also right around 10500! They got me another one and it was at 13500, right in the middle of the specs. Needless to say, I was glad I brought my ohmeter with me.

But this brought up some questions worth bringing to this tech forum:

1) Is this failure common?
2) Were they giving me the wrong coil?
3) Could a failing voltage regulator or some other component cause this failure?
4) Lastly, with my confidence low on the stock ignition components now, what is the logitical replacement ignition system

Thanks for the help

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Unread 09-26-2011, 11:35 AM   #2
toyotaSteve
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I would think the values measured do not indicate a coil failure; but the jeep started after it was replaced. I suggest keep looking the problem is not solved yet
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Unread 09-26-2011, 08:14 PM   #3
George Dickel
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I had weird ignition issues that were on-again, off-again in nature. I was convinced that it was the coil or a distributor issue (due to aftermarket camshaft). Nope, bad PCM! Got another one from a junkyard out of a rolled jeep shipped to me for $85. I'd try that and if it doesn't fix it, keep the PCM as an extra or sell that sucker. You'll be able to get your money back if you get a good deal to start with. If you do this, just match the code on the sticker on your stock PCM. Good luck...
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Unread 09-28-2011, 08:08 PM   #4
mnilsen
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Thanks so far...

Yes, I plan on carrying a replacement PCM with me from now on, as well as a coil. Going through the troubleshooting step by step without deviating, the only thing left was the PCM.

My only other guess was a faulty voltage regulator that might be causing the coil to fair...do you think this might be a possibility?
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Unread 09-28-2011, 09:06 PM   #5
NakedJeeper
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Do I understand correctly? The first failure was the OEM coil from 1999 that lasted 12 years? And then an aftermarkey one failed within a year?

I have a 98 and I replaced my OEM last year and the "New" one failed just a couple of weeks ago. I assumed the short life of the new coil was an indication of the inferior quality of the replacement part compared to the OEM part.



Coincidentally?? my Camshaft Position Sensor was also bad. Are the two failures related? I dunno..

If you find a real "Root cause" for your second coil failure, please let us know about it.
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Unread 02-06-2012, 12:12 PM   #6
MountainClimber
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Replace my ignition coil every 7k to 10k miles? This is so bad has gotten so bad that I have mounted a spare on the fender wall and extended the wires so that when it goes out all I do is change over the wires and ad a new one in the place of the old when I get home.
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Unread 02-07-2012, 07:21 AM   #7
mnilsen
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Yes, I now carry a spare in the Jeep for a change on the road as well. I have since then also replaced my PCM just because and carry the old one as a spare too.
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Unread 02-07-2012, 08:22 AM   #8
Wheelin98TJ
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A new coil from the dealer is only about $40 or so.

I wouldn't get an aftermarket part in this case. I once tried a non-OE coil and it did not last long at all.


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