How to tell if a ignition coil is going bad - Page 2 - JeepForum.com
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post #16 of 37 Old 05-30-2014, 10:52 AM
outofrng623
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Originally Posted by Gunrunner23 View Post
It's not THAT rough. Just not steady. But dips down to 350-400 rpm at some stops.
I know this thread is really old...just curious, did you resolve the issue? I have the same problem and horrible mileage (8mpg calc by hand)...I have gone through a lot of stuff to no avail. Thanks

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post #17 of 37 Old 07-18-2014, 04:44 AM Thread Starter
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Originally Posted by outofrng623 View Post

I know this thread is really old...just curious, did you resolve the issue? I have the same problem and horrible mileage (8mpg calc by hand)...I have gone through a lot of stuff to no avail. Thanks
I've had a friend with the same problem replace some o2 sensors and it fixed it. I don't have the money to throw down on o2 sensors right now so unjust live with it. Even though it's throwing a code for o2 sensor....

Recently after I start my wj, then drive for a bit and when I come to my first stop light it acts like it's gonna die when it's down shifting. It seems to only do any of this low rpm crap after down shifting. Like if I'm at a stop light and it goes down to 350-400 and I gas it a bit it will not drop back down again. Sometimes it will even correct itself.

I just live with it since its pretty common but not many people have fixed it. Aside from o2 sensors, transmission speed sensor, or clogged cat. But there have been people that have done the above and it didn't fix it so Idk.

2004 wj limited 4.7
IRO 3in lift with skyjacker hydro
265/75/16 TreadWright Claws
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post #18 of 37 Old 07-18-2014, 06:34 AM
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I have the same issues. Threw a lot of new things at it including o2s mopar. I am getting horrible mileage, stall maybe once every two months, just sitting idle even. Sometimes I idle at 700 sometimes 500. No logic. I've replaced the tps, iac, plugs, coils, exhaust including cats. No change. Fixed an exhaust leak. Still throw p0420 code, maybe another leak that wasn't seen? When it started happening I put in new o2s, three weeks later, same thing.
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post #19 of 37 Old 07-18-2014, 06:40 AM Thread Starter
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There's actually a reflash that I have read that helps. Some dealers do it free some don't. All of mine were going to charge me way too much. So F it.

Have u checked Ur injectors?

Fuel pressure?

2004 wj limited 4.7
IRO 3in lift with skyjacker hydro
265/75/16 TreadWright Claws
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post #20 of 37 Old 07-18-2014, 11:23 AM
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Fuel pressure has been checked and is fine. New pump as well. Injectors and compression are the only two things that haven't been done.
I find it odd that it only started after Having the exhaust done.
I've also heard about the reflash from a few people but see nothing in any of the tsbs for my year/engine. It also happened after I got the jeep, wasn't at acquisition. So if it needed a flash I would think it would've been a problem from day one. Maybe the actual PCM is going?
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post #21 of 37 Old 07-18-2014, 11:42 AM Thread Starter
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I'm not quite sure the reflash was really advertised. But I'm not guite sure. I've read that it's something that eventually needs to be done.

2004 wj limited 4.7
IRO 3in lift with skyjacker hydro
265/75/16 TreadWright Claws
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post #22 of 37 Old 07-19-2014, 07:52 PM
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There's a guy around me that does it for 125 I think. I also know an owner of a dealership, maybe he can get it done for me for nothing. I'll see. If I have to pay, I may be better off just getting a new PCM.
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post #23 of 37 Old 07-19-2014, 08:31 PM Thread Starter
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I'm pretty certain the tsb reflash will fix it.

2004 wj limited 4.7
IRO 3in lift with skyjacker hydro
265/75/16 TreadWright Claws
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post #24 of 37 Old 07-20-2014, 06:13 AM
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I just find it odd that it started happening after the exhaust was done...have had mileage issues for two years now...
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post #25 of 37 Old 07-20-2014, 06:45 AM Thread Starter
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That is weird although I can't see anything that would be a problem. I man aside from o2 sensors down there. You didn't put like 5inch pipes in did ya? Lol

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post #26 of 37 Old 07-20-2014, 11:38 AM
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I just find it odd that it started happening after the exhaust was done...have had mileage issues for two years now...
There is supposed to be a braided ground cable fastened to the exhaust system (somewhere near the cat or muffler IIRC). Did it get left off?
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post #27 of 37 Old 07-20-2014, 05:32 PM Thread Starter
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There is supposed to be a braided ground cable fastened to the exhaust system (somewhere near the cat or muffler IIRC). Did it get left off?
Mine came loose and was all rusted. It did all of the above. Before it got loose and I cut it off. I never reconnected mine so maybe, but it is a well known 4.7 problem. So surely it can't be one ground wire but ya never know!!

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post #28 of 37 Old 07-21-2014, 03:29 AM
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Took a look. Looks like the wonderful shop that did my exhaust neglected to put it back on. Not trying to be a Wiseass but is it really a known problem for the o2s and would throw this code and I have to wonder why only the one side. I'll see if there's enough to reattach otherwise I'll have to see if I can buy another one (I had replaced it once already) or make one. Ugh
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post #29 of 37 Old 07-21-2014, 04:50 AM Thread Starter
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Took a look. Looks like the wonderful shop that did my exhaust neglected to put it back on. Not trying to be a Wiseass but is it really a known problem for the o2s and would throw this code and I have to wonder why only the one side. I'll see if there's enough to reattach otherwise I'll have to see if I can buy another one (I had replaced it once already) or make one. Ugh
Well I should of clarified. The low idle is a known problem with the 4.7 with several different claimed fixes. Which are listed above. The reflash seems to be the end all fix; in other forums as well.

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IRO 3in lift with skyjacker hydro
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post #30 of 37 Old 07-21-2014, 07:36 PM
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Two round trip drives this week that would normally trigger the p0420...Did not. The only differences are, I put in a new battery (yes I have disconnected and reset prior to changing), so its not the reset, maybe the voltage...and I disconnected my obd2 scanner.
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