God Dang Misfire

[girthbrooks427]

Okay I will try to make a long story short I have a 07 Audi s6 5.2L v10. I purchased this car because the dealership I work out sent it wholesale due to supposed carbon build up that caused misfires at cold start up. I drove the car for probably a week before I fixed anything. The misfire was pretty prominent at cold start up and would then go away after it warmed up. So I did multiple carbon cleans (sucked through the intake) and it improved a lot. So I dug a little bit more on the internet and found that the pcv valve can cause my issue and are pretty common. Well my lower oil pan was leaking and I was slow at work so I figured I would knock that out. Resealed my oil pan and the check engine light went out by itself! Awesome im thinking as im waiting for my pcv valve to get here. Drove the car for a couple days and then my check engine light came back on and I started to leak some oil. Im assuming the oil pan go a hole sucked in it due to the bad pcv valve but I could be wrong. Replaced the oil pan gasket again and the pcv valve. Car ran great, probably the smoothest it has ever ran. This morning it was a little chilly and the car was missing for some reason. I pulled the codes. I will try to upload pictures. I have secondary air injection codes, mass air flow and 4 misfire codes, cylinder 7,3,4,9. Does anyone have any ideas or experience with a similar situation?

[girthbrooks427]

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[froggerS4]

The multiple misfires could be caused by the engine running lean. A couple of areas to look at that could cause a lean condition:
1. Bad or dirty MAF.
2. Vacuum leak in the intake somewhere.

I have an 08 S6 and had a leak at the throttle body connection. One of the bolts had sheared allowing air in to the system after the MAF ,which caused a lean condition. I don't think I got the MAF code as part of that, but it definitely resulted in consistent misfires in one cylinder and intermittent misfires in a few others.

Not sure what the SAI fault could be pointing to. If it's allowing air in to the exhaust system after the SAI is supposed to be off, then it could be confusing the exhaust O2 sensors. I would think the system would adjust to run rich to compensate though. My .02.

[girthbrooks427]

The multiple misfires could be caused by the engine running lean. A couple of areas to look at that could cause a lean condition:
1. Bad or dirty MAF.
2. Vacuum leak in the intake somewhere.

I have an 08 S6 and had a leak at the throttle body connection. One of the bolts had sheared allowing air in to the system after the MAF ,which caused a lean condition. I don't think I got the MAF code as part of that, but it definitely resulted in consistent misfires in one cylinder and intermittent misfires in a few others.

Not sure what the SAI fault could be pointing to. If it's allowing air in to the exhaust system after the SAI is supposed to be off, then it could be confusing the exhaust O2 sensors. I would think the system would adjust to run rich to compensate though. My .02.

Did yours go away after it warmed up? I was reading on Ross tech were a guy was having the same issue and he actually found that his coil connectors had broken clips and were lose and losing connection while cold and then as they warmed up the heat expansion made them swell and get connection thus the misfire going away.

[froggerS4]

Nope, didn't go away when warmed up, hence the search for the vacuum leak. We did a bunch of coil swaps, and spark plug swaps as well, but the misfires stayed on the same cylinders. I had also heard about that problem and verified that most of my connectors are still intact. Only two or three are broken. One fix for that problem is to loosen the screws holding the orange harness. This allows the harness to move somewhat independent of the block.

[girthbrooks427]

I made sure all my coils were connected and I tightened the little screw holding the harness after pushing it up so it would stay in place. I haven't had a miss fire in two days so I am keeping my fingers crossed. Also does anybody know where you can get the red connector if I was to want to repair the connectors? I can only find the black ones

[CBR900RRR]

I have multiple CEL with mis-fire codes, so far we have replaced plugs and coils, Valve Cover Gasket. next on my list is fuel injectors. most of my CELs come during hard acceleration.

[girthbrooks427]

you might check your pcv valve and possibly the connectors on your coil. My car also had misfire under hard acceleration but it went away after about 4 carbon clean can sucked through the intake.