2013 BMW 335i - Chronic Misfires under Load with P0300, P0301, P0306

Question

My F30 335i is throwing a 'Drivetrain Malfunction' on the iDrive every time I try to merge onto the highway or give it more than 50% throttle. If I baby it, it drives perfectly fine around town. As soon as boost hits, it starts bucking and goes into a limp state until I cycle the ignition.

I've got codes for random misfires and specific cylinders 1 and 6. I'm worried it's the High Pressure Fuel Pump (HPFP) failing since these N55s are known for it, but the car starts up instantly in the morning without any long cranking.

OldSchoolOtto · Answer

Check your walnut blasting history. The N55 is direct injected and the intake valves get coated in carbon over time. If the valves can't seal or the airflow is disrupted, you'll get those high-load misfires that feel like a fuel cut. If you haven't done it in 50k miles, it's time.

FreightlinerFred · Answer

✅ Confirmed fix: Diagnosed as failing ignition coils and improper spark plug gapping. Even though the coils were 'working' at idle, the high combustion pressures under boost were blowing out the spark. Replaced all 6 coils with Delphi units and re-gapped the new plugs to exactly 0.022" (stepped down from stock for better spark stability). The misfires under load are completely gone and the logs show zero timing corrections now.

2013 BMW 335i - Chronic Misfires under Load with P0300, P0301, P0306

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