'07 335i P0312E and P0174 with no P0171

[titandavid2008]

I have been getting misfire codes from cylinder 1, I did the whole switching the coils around to other cylinder to see if the misfire would follow, sometimes it does, sometimes it doesn't. Decided to go ahead and replace the coils and the spark plugs as I do not know when it had been done last if at all. I got the NGK's and the BAV Auto coils from ECS Tuning. Now it is throwing a P0312E and P0174. The reason I mention no P0171 is because that is what I keep getting asked when I mention P0174. I have called a few shops around me and they are just trying get me in the shop. I'm not driving it anywhere; so nobody is of any help.
For troubleshooting I have swapped the new coils out for the old ones; it runs just as rough, and I did reset the codes, they just came right back on. Went ahead and pulled the new spark plugs and verified the gaps on all 6. One thing to note though: ever since I changed out the coils and spark plugs, the engine has been running for less then 10 mins total time. When I pulled cylinder 1 the new spark plug was nasty looking, not wet at all, but dark brown and almost black. The other 5 are looking brand new. Thats as much as I can think of right now. I did a smoke test (hopefully I did it right) to see if maybe I messed something up, but that seemed to be fine. I'm looking for any and all ways I can troubleshoot this issue more. One thing I might do is call BMW and see what they think could be the problem. I'm really lost here.

[Greydog]

Welcome David

What your seeing are Generic codes you really need a BMW specific code reader like BMW 1.4.0, INPA, Autologic or similar they will be more specific in their description.

Regarding the codes your seeing they are associated with vacuum leaks 171 and 174 normally appear together which is why your being asked about 171 particularly as your engine is inline.

Have you checked for air and vacuum leaks include the crank case breather, I would also check the loom to the coils for any cracks or faults.

Dave