I Need Your Help Diagnosing a Problem

[VazzVenom]

I hope I'm posting this in the right place.... First a little background, my 2009 135i has 86,000 miles, MHD stage 1, no mods other than a muffler delete. Oil changed every 5000 miles, Spark plugs have ~20k on them. Haven't replaced coils since I bought the car at 52,000. Car has always had a fuel pressure sensor code and has had a decent amount of whitish, whispy smoke coming out of the exhaust. Not enough to alarm me but more than my Audi A4 that I had before this. I was told it was normal.

Now to my issues. I went to start my car the other day and it had a hesitant start and was running really rough. Tons of thick, white smoke coming out of the exhaust. It hung in the air and smelled like fuel (enough to burn my eyes in my garage.) Check engine light came on, scanned it, misfire on cylinders 2 and 3. Cut the car off, deleted the codes, started the car again and let it run. At first it was still rough but then it smoothed itself out to around 90% of what would be normal. Still had tons of white smoke coming out of the exhaust. This time didn't smell like fuel though, it smelled sweet like coolant. Alarms start going off in my head because I'm thinking head gasket. Long story short, I get it towed to a local shop that specializes in German cars. They thought it was bad seals in the turbos at first and the car had no misfire. Now the misfire is back and the car is blowing black/blue smoke. They're thinking it's an ignition issue and are trying to track down that fuel pressure sensor. What would you say is going on? I have my own ideas but it's all pretty speculative. I have more experience with NA cars. I'd appreciate any help I can get on this. Im renting a hatchback Ford Focus and I die a little every time I have to drive it. I miss my 1!

[velociti]

Probably worth replacing your spark plugs, but I doubt that they're the cause here, especially only running Stage 1 -- not too aggressive. My money's on the ignition coils. From my E46 M3 days, I was under the impression that coils either worked or they didn't, and you'd simply replace them as they failed. With these turbo motors with higher-than-stock boost levels, I'm getting the impression that might not be the case, and that while spark plugs are the first culprit, coils should be your second. With so much mileage (presumably on 86k-mile coils?) and you probably needing to do plugs anyway, I'd personally suggesting replacing all 6 spark plugs and coils and see if that fixes the issue. If not...may be an injector issue and someone else on here would have to speak to that.

For what it's worth, I've had misfires on a custom MHD tune that was attributed to spark plug gap not being tight enough (I had .026, while recommended is .018 for MHD from the looks of it), and despite trying OEM Bosch plugs and NGKs both gapped to .018, I'm still having "hesitation" issues. Only 41k miles, too. So I'd suggest at the very least replacing the coils on the cylinders that have misfires. I suspect that people may start replacing coils and not just plugs to sort out misfires going forward.

[MightyMouseTech]

My money would be on a leaking injector. Time for a set of -12s?

[VazzVenom]

Thanks for the help, guys. I'll relay the info to the mechanic and see what they say about it. I'll probably replace the coils soon even if that isn't the problem. I've been meaning to do it and have just prioritized other things.