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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. I have been clearing the code from the computer and going thru the drive cycle but the code returns.
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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Have you actually erased the code, cleared the computer and it keeps coming back?Or are you just throwing parts at it hoping the light will go off?
 

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How are you clearing the code? How soon does the code return?

You should try disconnecting the ground battery cable, and leave it disconnected for about 20 minutes..Then, hook it back up and take it around the block and see what happens.
 

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Discussion Starter #5
To get the check engine light to go off I disconnect the negative terminal on the battery for 15 minutes also turn and hold the key in the on position for 20 seconds.To clear the computer I have access to an OBD device and use the wireless app called Torque.
 

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Discussion Starter #7
First time it came on at 77 miles into a drive cycle, another was 60ish and one time I cleared it at night and did a cold start idle the next morning and it came on within 5 minutes.
 

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Hmm.. Have you took the air hat off and looked down into the TB? If there's a lot of oil in there, you have a blown plenum gasket and that could cause this problem too..

But for now, maybe you could go to the inspection place, park around the block, disconnect the battery to the clear code, then drive up and do the testing real quick while the light is off?
 

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Discussion Starter #9
I read that yesterday during my investigating and have yet to check on that.
As for disconnecting the battery... Been there, done that at 55 miles of a drive cycle. It will still be in the computers memory and they will see that. Also if I disconnect it, it comes up on their system that the computer is not ready because there are not enough miles on the system. Hence the need of the drive cycle. Can you start to feel my pain? LOL

Thank you for all your suggestions! I really appreciate.
M.
 

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I didn't know they went that deep into the inspection. You'd think if it's clear no codes, they say okay and move it along. We don't have inspections or none of that bullshit in Alabama. They don't even come outside and look at the car when you go to the courthouse or DMV to get a tag..lol

But back to your truck.. Is it running good even with the light coming on? it's not missing, low on power, nothing?
 

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Discussion Starter #11
Yeah, they're pretty strict here in Phoenix. They plug into your system and analyze everything. Bastards!
The truck: I owned the truck for 100,000 miles and not once changed anything on it. I'm a believer of "If ain't broke, don't fix it". But I was only getting 11.3 mpg and figured I'd work on getting that number back to normal so that's when I decided on replacing the electrical and doing so I got my mileage back to 15-16 mpg. The truck runs incredibly smooth. At traffic lights you can barely feel it running and picked up 40-50 miles per tank. It hasn't run like that in years due to my neglect. I don't feel any missing, low power etc... What I should do is either replace the #8 injector or swap it with another and see if the code follows that injector. That way I can rule out the injector. I also read to unplug electrical to the injector and see if the engine runs any different with it unplugged. If it runs rougher with it disconnected, it could be the injector.
 

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Yeah, clear the codes, swap injectors,and see what happens.

If you could get a new computer CHEAP, i'd try that out. Maybe you could find a place in town that could re-flash yours..
 

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Discussion Starter #13
Yep, that sounds like a plan. Unfortunately I'm out of town until Dec. 12th but I will be back on it when I get home.
I did find reprogrammed computers for $225 but that would be last gasp effort.
They will wave the test IF I spend over $450 on trying to fix the issue but I'll be back at it 2 years from now so I just want to fix it and be over it. Who likes driving with a CEL constantly on? Not me!

I'll keep you posted!
M.
 

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Swap the injector out before you lay out for the new computer. It's entirely possible that the coil has an intermittent short/open that is just enough to trigger the misfire code but not enough to throw the injector code - and you just aren't noticing the little stumble that would go along with it. I've got a bitchy injector in my truck, and sometimes I get the P0202 (injector circuit), sometimes I get the P0302 (misfire), and sometimes I get both.

I didn't know they went that deep into the inspection. You'd think if it's clear no codes, they say okay and move it along.
... And that's exactly why they check for system readiness - to see if you did just that.. Because it would defeat the entire purpose of doing the inspection if all you have to do to beat it is clear the codes around the corner from the station. :D And the system goes Not Ready whether you clear it with a scanner or by pulling the battery. Any state with OBD inspection checks system readiness.
 

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i'll add this here...

trace the wires coming from the injector all the way back to the PCM. during that, keep checking for any damage to the wire. i'm betting that it may need to be replaced or reconnected somewhere.

i give this suggestion because I've known of another case where someone was having an issue with a misfire.

deff swap injectors and see if it follows... be aware... that at your mileage you may need to get new O rings for the injectors due to them not sealing properly once messed with.

and i was being a smartass last night because i was stoopid tired lol
 

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Discussion Starter #16
Shokota, Misfit, TazRango,
Thank you all for your very good suggestions! I wish I was there to put them to the test! Shokota, thanks for the heads up on the o-rings. Something I definitely would've overlooked!
Keep the suggestions coming if you can think of anything else! I'll definitely keep this blog updated on the progress!
M.
 

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Discussion Starter #17
Hey Guys, I received this the other day...

Replace the cylinder head. The cylinder head crack between the valves and cause a misfire.
____________________________
Master Chassis tech, Transmission
Automatic and Manual and Suspensions.
Also repair front and rear diffs and all engine
repairs inc Diesel. A/C repair too.

I did some research on this and this could very possibly be my issue.
Summer 2008 (115*) I was driving up a steep hill, air conditioning on high in Yuma, AZ and had the plastic joint on top of the coolant line break on me. Instead of pulling over I figured I'd drive to the first exit (4 miles) thinking it was only a small break in the line. Of course I turned the heat on high and slowed to 30mph. I made it to the exit and when I got to the top the engine just quit. I thought, OH SHIT! Then when I opened the hood, I thought OH *UCK! The hose was completely separated. Meaning as the engine ran, the coolant was just running out of the engine. I thought for sure I seized the engine. Long story short... I may have cracked my head. Now my question to you guys since this guy isn't responding to my question. Is it possible to have a cracked head between the valves and still pass a compression test? Thoughts?
I've read that cracked heads on the 5.2 and 5.9 Magnum are as common as a crack on an ass.

Thanks,
M.
 

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The heads are known to crack... but plenty of ppl run cracked heads without misfire codes. (I think my truck may have cracked heads... just done let it know)

But the only way to tell is if you pull the head. The easiest thing to do is just live with the misfire.



I KID I KID, make a checklist of what we have suggested... you don't wanna go pulling heads unless you really need to.

I guess you could also check for exhaust fumes in the coolant (there is a tester for this) and have you noticed any smoke from your tailpipe?
 

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The 08 incident... did all of your troubles start just after that point?

Because we're almost into 2013... so if it is fairly new, I doubt the overheat was the killing factor. It may have been the start of an issue tho.
 

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Discussion Starter #20
Oh yeah, I'm still planning on pursuing all the other issues first and more if I can find out more info before pulling the head. Pulling the head is something I am not planning on doing in the near future. I will pay the amount needed to get the waiver ($450 worth of repairs) and that will buy me 2 years in which I will fix the issue.
As for the 08 incident... The truck ran fine after that and for the next 4-5yrs. Like I said, its getting better gas mileage that it has in years since I started working on it. And I probably will continue to drive it this way until I'm ready to spend the money. I did buy a 2005 5.7 Hemi 300C (mint condition w/44,000 miles) 2 weeks ago so I still have transportation. This all started when I changed the wires/plugs/cap/rotor/coil and Sea Foamed the system. And thanks for the exhaust fumes in the coolant suggestion! I will pursue that as well. And no, no smoke from the tailpipe. Clean exhaust!

So the saga continues...
Thanks Again!
M
 
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