pelletman

Good evening gentlemen.

I have a 2007 A8, 4.2, 155K with a P0303 misfire code. I pulled the coil and installed a new one, but the code is still there. It seems to run better, but not as smooth as it should. I should say it runs rough at idle a bit and under hard acceleration, almost shuddering I would say. When I clear the code it goes away for a bit, but if I accelerate hard it will pop up. I pulled the plug an it is the OEM plug and looks fine, nice light brown/gray color. I'd appreciate any input. Should I change plug? Change injector?

Also when I pulled the coil I see oil in the holes, which I cleaned out but I guess I am looking at a valve cover gasket job.

Thanks for your help!

pelletman

Aargh, somehow I posted twice, I hope a moderator can delete one of these!

Jack88

Could be due to carbon buildup, those are known for it. How did the spark plugs look?

Tstealth32

I have the same milage as you. Same thing, misfire on #4. Did a carbon cleaning, changed plugs and coils. Still had a misfire. Changed all the fuel injectors, misfire gone.

pelletman

Thanks! I changed the 4 plugs on that side, the originals seemed to be in fairly good condition. I swapped 1 and 3 coils misfire still in 3. I guess I need to change injectors. I'll search the forum to see if there is a how to do it thread.

Here are the plugs 1 is on the left, 2, 3, 4...

Thanks for the help!

pelletman

It looks like I need to pull the intake manifold? Probably should do valve cover gaskets and clean carbon? Should I replace all 8 or just the offending one? Thanks!

pelletman

Anyone have a list of things that should be done when doing this job? Maybe a parts list? Anyone ever try to clean injectors with this?

How to Clean Fuel Injectors in Your Car (Without Removal)

www.youtube.com/watch?v=bKGI9N_yWd0

pelletman

Also, just to be sure, the #3 is passenger side third back from the front?

pelletman

To wrap this one up, I ran a tank of 93 octane with Seafoam, a tank with Lucas, and a tank with BG44 and it cleared up the misfire, I am guessing cleaned the injector. I wasn't looking forward to pulling the injectors

Wachtel

how much of both did you use to stop the Misfire? I have a 07' A8 that is misfiring after plug and coil change.