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Unread 06-28-2012, 07:55 PM   #1
Gunrunner23
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How to tell if a ignition coil is going bad

My phone accidentally posted this in the wk threads. Is there a way to tell if a coil is going bad without a voltage meter? I looked on google but couldn't really find anything. Looked at a rx8 forum and something about a white scoring mark. Id buy 8 new ines but that's 160-200 dollars.

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Unread 06-28-2012, 08:41 PM   #2
boomersoonerGC
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If you can visually see they are bad then they are likely very bad. Its possible for them to get weak but you would need to test them with a multimeter.
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Unread 06-28-2012, 08:50 PM   #3
Gunrunner23
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I didn't know if there would be obvious scoring. Olive changed the plugs and remember the out side of one looking rough but didn't think anything of it. All the plugs were crap. Wish I remembered which one it was.
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Unread 06-28-2012, 08:53 PM   #4
Jacko84
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Do you have any symptoms?
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Unread 06-28-2012, 08:59 PM   #5
Gunrunner23
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Yeah fighting a rough idle and low idle when coming to a stop. I've done all the typical stuff. I've scanned and checked my rpm matching what the dash says.
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Unread 06-28-2012, 09:05 PM   #6
Jacko84
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What's the "typical stuff"? Sounds like your problem may be the TPS, IAC or you need to clean your throttle body. Visit this page for more info on how to take care of those 3 things: http://wjjeeps.com/service/tbody.htm
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[B][url="http://www.jeepforum.com/forum/f310/ultimate-wj-grand-cherokee-buyers-guide-1271979/"]The Ultimate WJ Grand Cherokee Buyer's Guide
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Unread 06-28-2012, 09:16 PM   #7
Gunrunner23
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Yeah that's the typical stuff. I've been there some that... took of the tv cleaned it. Cleailned IAC replaced the TPS checked map replaces fuel filter. Ran scanner tool.
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Unread 06-28-2012, 09:17 PM   #8
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Sorry damn phone auto correct. Been there done that** And TB**
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Unread 06-28-2012, 09:22 PM   #9
Jacko84
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Sometimes just cleaning the IAC doesn't do it, may need a new one i had similar symptoms in my 4.7L HO, at stop lights the rpms would drop and idle rough, I got an aftermarket TPS a few months ago and it was good for a few weeks, then the symptoms were back. 3 weeks ago I got a MOPAR TPS and it's back to normal idle and no kore drops in rpm. I've heard a lot of folks having issues with off brand sensors. Have you replaced your plugs? Is it a regular 4.7L or the HO?
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Unread 06-28-2012, 09:29 PM   #10
Gunrunner23
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Regular. I replaced them a month ago. I opted for a bwd because bord-warner is a pretty good brand. Plus 1 year warranty.
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Unread 06-28-2012, 09:44 PM   #11
boomersoonerGC
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BWD has done nothing good on my WJ. Every single BWD sensor has been replaced by Mopar and gotten much better results.

Mopar parts, if purchased from an authorized dealer, offer a 12mo 12000mi warranty too.
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Unread 06-28-2012, 09:45 PM   #12
Jacko84
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Quote:
Originally Posted by boomersoonerGC View Post
BWD has done nothing good on my WJ. Every single BWD sensor has been replaced by Mopar and gotten much better results.

Mopar parts, if purchased from an authorized dealer, offer a 12mo 12000mi warranty too.
^^ this!
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[B][url="http://www.jeepforum.com/forum/f310/ultimate-wj-grand-cherokee-buyers-guide-1271979/"]The Ultimate WJ Grand Cherokee Buyer's Guide
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Unread 06-28-2012, 09:48 PM   #13
Gunrunner23
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Its my understanding that a bad TPS jacks the rpms way up. Which is why I was gonna buy a IAC tomorrow.
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Unread 06-28-2012, 09:56 PM   #14
Jacko84
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Quote:
Originally Posted by Gunrunner23 View Post
Its my understanding that a bad TPS jacks the rpms way up. Which is why I was gonna buy a IAC tomorrow.
Not necessarily... Just rough idle in general for most people
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[B][url="http://www.jeepforum.com/forum/f310/ultimate-wj-grand-cherokee-buyers-guide-1271979/"]The Ultimate WJ Grand Cherokee Buyer's Guide
[/url][/B]
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[COLOR="YellowGreen"][B][url="http://www.jeepforum.com/forum/f348/north-texas-grands-1323367/"]North Texas Grands[/url][/B][/COLOR]

[COLOR="DarkRed"][SIZE="4"][url="http://www.jeepforum.com/forum/f22/jacko84s-wj-build-thread-1398349/#post13930247"]Jacko84's build thread[/url][/SIZE][/COLOR]
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Unread 06-28-2012, 10:09 PM   #15
Gunrunner23
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It's not THAT rough. Just not steady. But dips down to 350-400 rpm at some stops.
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