Durango misfire after plug and coil pack

Tiny
POOL_PLAYR
  • MEMBER
  • 2005 DODGE DURANGO
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 69,000 MILES
Hey all, I have a 2005 Dodge Durango, 3.7 V6, with a misfire problem that has been haunting me for almost a year. It comes and goes. The first time was a coil pack fixed the problem. Over the last 8 months or so, it starts missing randomly and stops after a few days. It has gotten really bad over the last few weeks. It kept giving either a cylinder 3 or 4 misfire (5 once as well, I believe). I replaced the spark plugs, and 2 more coil packs, and drove great for about 2 weeks. Now its missing worse and more than ever (before only when warm). The engine light finally came on today, and its reading cylinder 4 AGAIN. This cylinder has a new plug and coil pack. I also re-arranged the injectors over the last few weeks. WHAT is causing this?
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Wednesday, November 17th, 2010 AT 12:52 AM

4 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
When you remove the plug, what does it look like? Is it wet, oil fouled? Have you checked the crank sensor to make sure it is in good shape as well as the coil wires? You could have a break in the insulation causing the problem. Check them for continunity all the way back to the PCM. While checking, move the wires around to see if they cause a change in resistance.

If all that is good, we need to check compression in that cylender.

Let me know what you find.
Joe
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Wednesday, November 17th, 2010 AT 1:17 AM
Tiny
POOL_PLAYR
  • MEMBER
The plug looks fine, as well as the wires/electrical plug that plugs into the coil pack. I have been thinking about the crank sensor as well, but I believe that will trip its own code, won't it? Whenever it starts misfiring, it trips the same cylinder number for a few days and randomly changes to another. I was a tech for GM 6 years ago, but did more steering/suspension/brakes than other repairs so I have a good knowledge of autos but am just a little rusty on the self-diagnosis end of it. I miss all the special equipment the dealer suppied!
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Wednesday, November 17th, 2010 AT 1:26 AM
Tiny
BMRFIXIT
  • EXPERT
Remove the injector and rail and check for dirt
very common
Never seen a random misfire that comes and go caused by a bad crank sensor
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Wednesday, November 17th, 2010 AT 1:54 AM
Tiny
POOL_PLAYR
  • MEMBER
When I swapped the injectors between cylinders a couple weeks ago there was no dirt or grime past the o-rings on any of them. They looked good/clean.

Up until this weeks episode, it only missfired when the engine was warm, and got significantly worse if I was driving around town for an extended period of time. After I replaced the spark plugs (that were only 6 months old)it ran like new. Now after 2 weeks of it driving fine, it has started acting up again, but now its missing from the second I crank it up in the morning. It makes me think that it was coincidence that it stopped when I changed the plugs. Because of the history of this problem over the last 8 months (only missfires for a few days then goes away as randomly as it started). But now that it is coming and going every few weeks instead of every few months, it makes me think that I have a part/sensor on its last leg thats either about to or already has completely burnt out or failed. During the older episodes, it acted up more at half to full throttle and was fine at lower rpm's. Now any throttle, unless absolutly babying it, makes it act up. And if it helps, after I ran the AC for 10 min the other day the misfire got almost twice as bad even after I turned the AC off and has stayed this way.

I have too much pride to take it to a shop, and I am very mechanically inclined, but this issue has me stumped.

SO. The plugs are new/look good, there is a new coil pack on the current problem cylinder, the injectors looked good and were swapped around, and I've owned this truck for over 2 years of its 5 year life and put over half the miles on it and have taken good care of it during this time.

Anyone have any personal experiences with this SUV/motor that might stand out in this situation? Or any other ideas?
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Wednesday, November 17th, 2010 AT 2:54 AM

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