P0308

fire101fighter · Nov 2, 2016

Went to remote start the truck today after work and got the single beep saying it wasn't going to. So I figured I was low on fuel or something. Got in the truck and started it, cranked no problem, then the check engine light came on. Got home, no issues with running rough or sluggish. Ran the code and came up cylinder 8 misfire. Cleared it and drove it around the neighbor hood no problems, no light. Any idea what could've caused it? Just a fluke?

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savage_46 · Nov 2, 2016

Worn spark plugs, bad coil, bad injector, bad fuel. Those are the usual culprits. Depending on mileage, could be carbon build up or possible mechanical issue. There's also been pcm updates released for many newer Chrysler vehicles that address P030x.

My last truck had a misfire from the factory, not bad enough to set a DTC, but noticeable at idle. Bad fuel with high ethanol set a misfire DTC on remote start which ended up being a bad injector.

Hootbro · Nov 3, 2016

^^^^^^^^^

What he said.

I would also add that if you are going to the trouble to check or replace the plugs, to swap the coil pack from the #8 cylinder with another and monitor to see if the problem travels or not.

mtofell · Nov 3, 2016

I'd probably just run with it for a bit and see if it comes back on. I've had codes appear and not come back after being cleared. With all the sensors these trucks have its amazing we don't get error lights popping every day.

fire101fighter · Nov 3, 2016

Yeah gonna try the plugs. Cleared the code yesterday and it came back on today. Gotta do the passenger side exhaust manifold bolts this weekend so mind as well do the plugs while we're in there.

CherryRed · Nov 3, 2016

Those back plugs are easier to access with the fender liners removed....

fire101fighter · Nov 13, 2016

Plugs replaced yesterday, with the factory NGK plugs, check engine light came back on again. Gonna scan the code today

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fire101fighter · Dec 4, 2016

Ok guys, still having the issue. Plugs were replaced and code cleared. Came back on, again for cylinder 8 misfire. Cleared the code and moved the coil to cylinder 4. Also did the passenger side exhaust manifold as it was warped and 2 studs were snapped. Drove for a few days and the friggin light is back on, same code, and it's still saying cylinder 8 misfire. What's the next step? And ideas?

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fire101fighter · Dec 4, 2016

Also, the truck doesn't run or idle rough at all. In fact, it's running better than ever. And it seems that it only throws the code when the remote start is used, sometimes after almost 10 minutes other times after about 45 seconds

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savage_46 · Dec 4, 2016

Pcm up to date? What year & engine? I can check tsb's tomorrow

fire101fighter · Dec 4, 2016

It's should be up to date, haven't had it to the dealer at all. 2010 ram 1500 with the 5.7, with 77,000 miles.

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fire101fighter · Dec 4, 2016

I'd appreciate it savage

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Hootbro · Dec 4, 2016

fire101fighter said:
Ok guys, still having the issue. Plugs were replaced and code cleared. Came back on, again for cylinder 8 misfire. Cleared the code and moved the coil to cylinder 4. Also did the passenger side exhaust manifold as it was warped and 2 studs were snapped. Drove for a few days and the friggin light is back on, same code, and it's still saying cylinder 8 misfire. What's the next step? And ideas?

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With what you have already done, I think you are either looking at either fuel injector, fuel injector control or valve issues.

fire101fighter · Dec 4, 2016

I'm seriously hoping it's either an injector or the control and not a valve. With a valve issue, would there be any tapping or other noise, symptom? Coincidentally, cylinder 8 is the cylinder where the exhaust manifold studs were snapped.

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Hootbro · Dec 4, 2016

fire101fighter said:
I'm seriously hoping it's either an injector or the control and not a valve. With a valve issue, would there be any tapping or other noise, symptom? Coincidentally, cylinder 8 is the cylinder where the exhaust manifold studs were snapped.

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There was another thread around here where someone had random misfires and had valve issues but it was also audible. I have also read of instances that if a big enough chuck on carbon breaks off, it can lodge in the valve seat and not let a valve seat properly and cause a random misfire.

Also, even though coils were swapped, I still would not rule out a coil control issue with the PCM. Really need a pro with a scoped meter tool to check both coil firing pulses and fuel injector pulses to see if it is a wiring issue or possible PCM issue.

Only other hot swapping to see if problem travels is swapping a fuel injector. Anything else is going to need someone with a scope tool and the knowledge to operate it.

fire101fighter · Dec 4, 2016

Yeah, going to swap injectors over the next day or two. Thanks for the input

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savage_46 · Dec 4, 2016

Got bored & just checked. There are 5 tsb's for pcm updates with various drivability & trans improvements. Quick search for 308 & it doesn't appear that any of the updates mention that code. I'm on my phone with painfully slow Internet, I'll dig a little deeper tomorrow. If you're still covered under extended federal emissions (8/80 iirc), a pcm update would be covered.

fire101fighter · Dec 4, 2016

Copy, thanks

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fire101fighter · Dec 4, 2016

Just a long shot, but I'm coming up on my oil change. The oil level isn't low, but could that maybe affect it?

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Hootbro · Dec 5, 2016

fire101fighter said:
Just a long shot, but I'm coming up on my oil change. The oil level isn't low, but could that maybe affect it?

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No relationship there to be plausible.

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