Hoping someone (Nathan :) ) can help me out here. I'm getting a cylinder 6 misfire error code on my 07 e92 N51 with 155k miles. It's a SULEV car in a SULEV state but unfortunately it's over the 150k warranty. The error code only occurs when I initially start the car in the morning or with very spirited driving. I erase the code each day after initial start and then it always reappears the next day (or again, after spiriting driving). It's also the only code I get. I swapped coils and changed the spark plugs and the error stayed with cylinder six. So I took the car to the stealership - after digging around they believe it to be the exhaust lifters that are sticking at cold start - a very expensive (most of it labor) job for a car with 155k miles. So I put in some Marvel Mystery oil without any luck. I then tried the Liqui Moly products - engine flush, lifter stuff and Ceratec. No change (figure all worth a try considering the cost vs. the alternative).
So the I went to a reputable BMW specific independent shop for another opinion. They did the usual tests just like the stealership - started with swapping coils, then plugs, then compression test but were ultimately perplexed by the issue. Though they didn't believe it to be a lifter issue and suspected that its more of a fuel delivery issue. However, they didn't know definitively (after visually looking at the fuel pump) either way and figured the only way to solve the issue was to start throwing parts at it, which they didn't want to do given the uncertainty of the fix. Of note, the car also had a fuel pump replacement done about four years ago under the previous owner at some mom and pop shop. Any thoughts?
I planned on keeping the car (as I do most of my own maintenance) and take care of it but this problem is getting quite annoying. I can still drive it but the CEL comes up with spirited driving, so if that's gonna be the case I'd rather dump it. Unfortunately I can only trade it in to a dealer at this point at a deep discount. Any help is much appreciated.