P0304
HighP0304 — Cylinder 4 Misfire Detected
Description
What This Code Means
The DME detects misfires in cylinder 4. Typical causes are the ignition coil, spark plug, or fuel injector. On N55 engines, the coils are a known weak point and often fail, especially on tuned (chipped) motors.
Symptoms
Symptoms
- Check Engine Light on the instrument cluster
- Rough idle
- Loss of power
- Vibration
- Possible transition to limp mode
Causes and fixes
Diagnosis and Repair
- Swap the ignition coil from cylinder 4 to another cylinder. If the misfire follows the coil, replace it (OEM
12138616153). - Inspect the spark plug in cylinder 4 (OEM
12120037563). - Check the fuel injector in cylinder 4.
- Perform a compression test if needed.
Possible secondary damage
Secondary Damage
Ignoring misfires can lead to:
- catalytic converter damage;
- oxygen sensor contamination;
- cylinder wall wear.