Ignition Misfire
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Ignition misfire occurs when one or more cylinders fail to fire properly, caused by worn spark plugs, failing ignition coils, or ignition system faults. The engine cannot burn fuel in those cylinders, leading to rough running and shaking. On BMW, this ranks among the top causes of idle vibration and drivability complaints, especially when paired with a flashing check-engine light or stored misfire codes.
What it feels like
You'll notice a distinct rough, shaky feel at idle or under light acceleration. The engine may vibrate through the steering wheel, dashboard, or seat. Some owners describe it as a violent shaking or pulsing sensation that worsens when stopped at a traffic light. The shaking often improves or disappears during hard acceleration. A flashing check-engine light usually appears alongside the symptom, signaling that the engine computer has detected a misfire. In severe cases, you may also smell unburned fuel or see black exhaust smoke.
How to confirm it
- Connect a diagnostic scanner to the OBD port and retrieve all stored and pending fault codes. Look specifically for cylinder-specific misfire codes (P0301 through P0308), which point directly to ignition or fuel delivery faults.
- Remove and inspect each spark plug in sequence. Check for worn electrodes, heavy carbon or oil fouling, and incorrect gap spacing. Oil-fouled plugs suggest a valve cover gasket leak; worn plugs indicate normal wear-out.
- Swap ignition coils between two cylinders, then rescan for codes. If the misfire code moves to the other cylinder, the coil is faulty. If it stays on the original cylinder, the fault is likely the spark plug or fuel injector.
- Inspect the spark plug wells and valve cover for oil seepage. Oil contamination on the plugs or inside the wells points to a leaking valve cover gasket that must be addressed before the new plugs will stay clean.
Parts that fix it
Replacement ignition coils and spark plugs together restore proper combustion. Match the kit to your engine code and model year.
Eldor Ignition Coils & Bosch Spark Plugs Tune-Up Kit for BMW N55 by LAIPZ - $249.35. Complete coil and plug set matched to the N55 six-cylinder engine found in 335i, 535i, and X5 models.
Genuine BMW High Power Spark Plug Set 8pcs for X5 X6 E70 E71 F15 F16 by Genuine BMW - $220.49. OEM plugs for the E70/E71 X5 and X6 models and newer F15/F16 generation X5.
NGK Ignition Coils & V-Power Spark Plugs Kit for BMW E39/E46/E53/E60/E83 L6 by Newparts - $217.95. Fits E39 5-series, E46 3-series, E53 X5, E60 5-series, and E83 X3 with six-cylinder engines.
Genuine BMW High Power Spark Plug Set 8pcs for E70 E71 E72 F01 by Genuine BMW - $201.97. OEM spark plugs for E70/E71 X5, E72 X6, and F01 7-series models.
Mishimoto Ignition Coil Set for BMW M54/N52/N54/N55/S54 2002+ by Mishimoto - $165.95. Coil pack set covering a wide range of naturally aspirated and turbocharged inline-six engines.
BMW N20 Ignition Coil and NGK Plug Set for BMW by BMW - $103.51. Genuine paired coil and plug set for the N20 four-cylinder turbocharged engine in 320i and 328i models.
Sources
- https://www.bimmerforums.com/forum/showthread.php?2076161-328i-Engine-shaking-violenlty-and-check-engine-light
- https://www.1addicts.com/forums/showthread.php?t=596097