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Discussion Starter #1 (Edited)
Issue: P0308 code.
I have a P0308 code/#8 misfire that will NOT go away!
I've read what seems like every page on the internet about this code but nothing seems to be working. I installed new coil, wires, plugs, cap and rotor. Swapped out #8 plug and wire, still got it. Next up, compression test... all came back fine. Low 155, High 170. Sprayed carb cleaner looking for vacuum leaks, found nothing. Ran Sea Foam thru vacuum, gas and oil (idled 15 minutes before oil change) made it run much smoother but still got the code. Injector seems to be working fine as well. Replaced upper and lower o2 sensors.
Being so frustrated, I broke down and paid $104.00 (*for nothing!) and took it to the Dodge Dealership. They had it for 2 days and also could not find the issue. They said everything seems to be working perfect for a truck that has 130,000 miles. They suggested that I replace the ECM/ECU but they weren't making any promises that that would be the issue. *Thanks for nothing guys!
Anyways, I'm at wits end on this and have to pass an emissions test ASAP. Any thoughts would be greatly appreciated.

Thank you in advance!
M.
 

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The Anti-RUB
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1,752 Posts
I assume you verified that you are getting spark at that cylinder. How did you test the fuel injector? The injector could be bad or not getting power/ground to open & close. Rent a noir light kit from your local auto parts store and make sure the fuel injector is getting commanded on/off like the others. Might also try swapping the injector with an injector from a different cylinder and see if the trouble code follows the injector.

If there are not drivability issues, and the motor doesn’t stumble or shake like there is a misfire, try resetting the code and see if it comes back.
 

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Discussion Starter #3
Petrock,
Thank you for the advice. I did swap #8 injector with #2 and I'm still receiving the p0308 code. I did have another person suggest rerouting my spark plug wires and that seemed to help and I thought that it was this issue. After rerouting the wires, the CEL light went off within 30 minutes of driving it. Thought I fixed the problem. BUT now I am NOT getting the CEL turning on but I still have the p0308 code showing up in the computer. I have been clearing it from the computer but when I retest, its there! Grrrr!
I feel like I've done every test in the book. I'm still concerned it is a crack in the head. I had the dealership and myself do compressions tests that have passed and I've done the exhaust in the coolant test but I'm still not confidant in those tests. I saw another way of checking by blowing air into the #8 cylinder using the compression tester and seeing if bubble appear in the radiator.
Also, I am not experiencing any drivability issues as I just drove from AZ to CA last night and got the best gas mileage in years. (14.3hwy) The only thing I feel is a rough cold idle at 600 rpm. When its warm, you can barely tell the truck is running its so smooth.
Any other thoughts would be appreciated.
 

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The Anti-RUB
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BUT now I am NOT getting the CEL turning on but I still have the p0308 code showing up in the computer. I have been clearing it from the computer but when I retest, its there! Grrrr!
The CEL only turn on when the computer detects the same code multiple times within some set amount of time. So the problem isn’t really fixed. You only made it happen a lot less then it used to.



When its warm, you can barely tell the truck is running its so smooth.
It sounds like you have an intermittent fault, which would point to an electrical problem not mechanical. Try testing the cyl #8 fuel injector circuit. I recently wrote a writeup on how to test a fuel injectors circuit with a volt/multi-meter. It may reveal the problem: http://www.dakota-durango.com/forum/showpost.php?p=3032440&postcount=3. The only addition I would make to my writ up for your problem is when testing the power wire, snap the throttle a couple times to see if the voltage drops/changes. It should stay at constant battery voltage.
 
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