Chasing a frustrating misfire issue on my BMW E92 335i (N54) that started immediately after doing a valve cover gasket.
Symptoms:
- Rough idle + misfires across multiple cylinders (mainly seems clustered around 1–3)
- Multiple injector-related fault codes (including 30BA showing up intermittently)
- No issues before the valve cover job
- Coil + spark plug swaps done → no change in symptoms (misfire doesn’t follow parts)
Recent work:
- Valve cover gasket replacement
- Fuel rail / injector area was disturbed during the job
What’s been ruled out so far:
- Ignition (coils + plugs swapped, no change)
Current theories:
- Injector connectors not seated properly / wiring issue from valve cover job
- Fuel rail or high pressure line seating issue
- Injector issue affecting multiple cylinders
- Some people suggesting DME output stage (MOSFET failure), but unsure how likely that is given it started right after mechanical work
Question:
Does this sound more like a disturbed wiring/fuel delivery issue from the valve cover job, or is DME failure (MOSFET/output stage) actually realistic in a scenario like this?
Trying to avoid throwing parts at it, just want to narrow it down logically before going further.
u/Important-Funny-6093 — 14 days ago