Need some help (severe misfiring)

[Zreed117]

Hey ya'll,

2011 BMW 335XI e90 N55. Severe engine break up at anything over 3/4s throttle. Drives perfectly normal in everyday traffic. Started happening after running MHD e30 tune for the first time right after replacing my valve cover and spark plugs with NGK SILZKBR8D8S (gapped way too big, recently corrected but plugs are already pure white). Here is a data log with a 2nd and 3rd gear pulls, its horrible but hopefully someone can help identify something. I fear that its a severe lean condition and dont want to hold full throttle for too long. https://www.spoolstreet.com/graphs/log-03-18-2025-13-19-18.46150/?series=2,10&zoom=-7,719

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[baronmellick]

When your on throttle your AFR looks fine, rail pressure is okay and there aren't excessive timing corrections for any cylinders, id check for a vacuum leak (smoke test) and I noticed you didn't have a bank 2 lambda reading. Could be an O2 sensor. Do you have any codes.

 

[Zreed117]

When your on throttle your AFR looks fine, rail pressure is okay and there aren't excessive timing corrections for any cylinders, id check for a vacuum leak (smoke test) and I noticed you didn't have a bank 2 lambda reading. Could be an O2 sensor. Do you have any codes.

Both o2s were recently replaced along with the vrsf downpipe but I will double check wiring connections. No codes, pending or permanent however I did have these pop up before I fixed the spark plug gap. Similar symptoms as well:
28A0 - Air mass system, plausibility: calculated air volumes in air intake system implausible.
2EE0 - Combustion misfires, several cylinders: Fuel injection deactivation.
2EE7 - Combustion misfire, cylinder 2: Fuel injection deactivation.
2EFE - Combustion misfires, several cylinders: Damaging to catalytic converter or damaging exhaust gas.
2F00 - Combustion misfire, cylinder 2: Damaging to catalytic converter or damaging exhaust gas.
387F - Power management: Standby current violation.

 

[baronmellick]

The damage to Cat codes are a result of a misfire under load that is so bad the the DME is cutting fuel to not damage the catalytic converter. Since the only direct cylinder misfire code is cylinder 2, swap coil packs and plugs, from 2 to another cylinder and see if the misfire follows. If it does not, you likely have a compression issue or a stuck open or leaking injector. Id also recommend smoke testing the vacuum system. Even though you are hitting boost target, a leak can cause your TMAP to read incorrectly (Your 28A0 Code). 387F is unrelated, it just means your battery drains more voltage when the car is off than what is normal. Id swap coils, clear codes, and data log the car again and see what happens. Best of luck!

 

[ShocknAwe]

Have you flashed back to stock? Start there.