Bmw 318i n46 engine misfiring, HELP!!!!
BMW E90 318i (2006, N46) – P0304 Misfire only at idle when engine is warm I'm hoping someone can point me in the right direction because I'm running out of ideas. Car: BMW E90 318i 2006 (N46B20) Symptoms: P0304 (Cylinder 4 misfire) Misfires only at idle Runs perfectly fine when driving Only starts misfiring once the engine reaches normal operating temperature Cold start and cold idle are smooth What I've already done: Replaced injector #4 with a known good injector Spark plugs are almost new Ignition coils are almost new Misfire is still only on cylinder 4 The engine idles smoothly when cold, but once it's fully warmed up, cylinder 4 starts misfiring at idle. Under throttle or while driving it feels normal. Could this be a vacuum leak around cylinder 4, a compression/valve issue, injector wiring, or something related to VANOS or Valvetronic? Has anyone experienced this exact symptom on an N46? Any advice on what I should test next would be greatly appreciated