P0308 - Misfire in Cylinder 8

Just in the last month this code keeps coming up. I have taken the car to the dealer twice now. First time they thought it was bad gas. So I burned through the tank and went to a different station. I always run premium. But the code came back.

Brought it in a second time and the manager says it might be related to the Ford Performance Pack 1 Tune on the car. I am skeptical about this as this is a tested conservative tune by Ford and it's been on the car since the beginning of the year. This problem only just started happening in the last month. Supposedly they swapped some coil packs around to see if the error points to another cylinder and then sent me on my way. Since then it's come back 4 times, and always the same P0308 code. No other codes that I have seen.

Has anyone had this issue? I do feel some hesitation here and there but at this point I am not sure if it's just my mind playing tricks. It idles OK. I have to take it back to the dealer but they seem to be stumped so I am hoping someone else who knows of this issue might be able to offer some suggestions.

Dealing with it now 2nd time, first time it was p300, p305, p308. Dealer downloaded firmware. Now they are saying onw bank is contaminated. Found black particles in the fuel sample..

you may have a cracked intake manifold or possibly a bad valve/piston. other people in the forums have had issues with cyl8 code due to a cracked intake manifold.

Mine cracked the valve spring at about 100 miles.

I requested they check the manifold. Right now, due to contamination in the fuel replacemwnt parts are 3 fuel pumps (filtwrs are not serviceable), clean tank and lines and replace 8 injectors, $1500... the tech spent time with me yesterday goi ng over everything, the tank was dirty, i saw it for myself. The fuel rail design allows sediments to migrate to the left bank. Ill post results of the manifold inspection.

Thank you for the input everyone. I plan to take the car to a different dealership this time around.

Looks like the intake manifold is a big area to look. Let me know how it turns out for you Mvalenti.

They agreed to check the manifold. However im not off rhe hook for the bad fuel...

Welp, one interior panel isnt fitting properly, tech agreed, also, they screatched my bumper in 3 places removing the tail lights. Slight gas smell in cabin... I'll keep you posted...

I have the same issue.


First issue I had with the car was having it die on me when pushing the clutch in. Happened twice. This was several thousand miles ago (car is at 14500 after a long 3000 mile trip recently, and Ive had it since February).


Some time after that happened, (I dont necessarily think they're related, just giving all info) I had a CEL come on. P0300, P0307, P0308. Took it to the dealer and they claimed the MAF was dirty (Steeda ProFlow CAI was the only thing Id done to the car at the time). They cleaned it and said it was fixed.


About 100 miles later, it came back. Took it in again. Told them to check the intake manifold since I saw a lot of mention of cracked manifolds on here causing this issue. Blah blah we can't go by what anyone says on the forums, and we don't see this issue on official ford forums speech. They check anyways and say its fine, however now claim it has a bad health monitor or whatever giving off false codes. Sure, whatever. I have that 3000 mile trip coming up the following day.


About 200 miles into the trip, the CEL comes back on. Big surprise. I get to my destination where Im doing a bunch of work (headers, exhaust, tune, short throw shifter, transmission fluid, thermostat) and drive back. During this time the light came and went. I found that the misfires happen right around 1900 RPM (65 in 6th). I didn't notice this at first because doing 65 on I-10 is ridiculously !@%$ing slow. After a speeding ticket, I decided Id just keep cruise control on on the way back.. thats when I noticed I could get the CEL to flash whenever I wanted a break in the boredom of the southwest.


Im taking it to another dealership tomorrow, because I dont trust the competency of the one I've been taking it to. They stole two OBD2 readers from my car I traded in while it was on their lot waiting for me to get my stuff out of it.. I didn't fight it because I'd like to have a good relationship with the people that will be working on my modified car. They however have fought me on everything I've taken to them, and seem to fail at their job every time.


Now I just need to figure out how to get ford to pay for the rental I will require to complete my 130 mile round trip between home (near crappy dealer) and work (dealer that seemed to know what they were doing with my last car).


Such a massive pain in the ass for a 6 month old car.

53 miles since service, light back on p308 code, csmera acting up again

Mvalenti said:

53 miles since service, light back on p308 code, csmera acting up again

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Did they check the intake manifold?

My CEL has turned off but last time they said after 12 key cycles it would. Still plan to go on Sat to a different dealer and have them take a look. The codes are still stored.

Other than tank issues etc you are going through, we've seen lots of those same CEL's here when the car is modified and tuned. We've traced about 20 cars down to either the tune setting for O2's, or the O2's themselves.

Good luck with it...

I had an intermittent misfire on cyls 4 and 8. It would happen when holding the rpms over 3k but could make it stop by shifting out of that rpm zone. See post #29 for video: http://www.mustang6g.com/forums/showthread.php?t=52589&page=2

The injector driver in the PCM was determined to be failing. 2nd dealer replaced the PCM under warranty and it's been running fine for over a year. This is after the first dealer threw new injectors, rails, and plugs at it then began flashing the computer so the code would go away. The car only had suspension and exhaust back then, it's since been tuned and runs on 93 and e85 without issue.

No mods to my car, its stock. I spome with the tech about intake manifold crack, he sprayed brake clean on all the runners with the engine running, no change in rpms. Talked to service manager today. Bringing car in tuesday. Mentioned upset by 1400 bill i paid and issue is still there..

Mvalenti said:

No mods to my car, its stock. I spome with the tech about intake manifold crack, he sprayed brake clean on all the runners with the engine running, no change in rpms. Talked to service manager today. Bringing car in tuesday. Mentioned upset by 1400 bill i paid and issue is still there..

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if you have junk in the tank have to talked to the Station where you fill up?