how to resolve P0301 misfire code in my BMW 5 Series F10/F11 (2010-2017)?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil:
  • Disconnect the electrical connector from the ignition coil.
  • Remove the bolts securing the ignition coil using a socket set.
  • Carefully pull the ignition coil out of the spark plug well.
• Remove the spark plug:
  • Use a spark plug socket to unscrew the spark plug from cylinder 1.
  • Inspect the spark plug for condition; replace if worn or fouled.
  • Ensure the new spark plug is gapped to the manufacturer's specifications (typically around 0.032-0.036 inches).
• Install the new spark plug:
  • Screw in the new spark plug by hand to avoid cross-threading, then tighten to the torque specification (usually around 15-20 Nm).
• Reinstall the ignition coil:
  • Insert the ignition coil back into the spark plug well and secure it with bolts.
  • Reconnect the electrical connector.

3. Test Ignition Coil

• If the spark plug was not the issue, test the ignition coil:
  • Replace the ignition coil with a known good one or swap it with another cylinder's coil.
  • Clear the error codes and start the engine to see if the misfire persists in cylinder 1.

4. Inspect Fuel Injector

• If the misfire continues, inspect the fuel injector:
  • Disconnect the fuel injector electrical connector and remove any mounting bolts.
  • Replace the injector with a new one if it is defective or clogged.
  • Reconnect the fuel injector and ensure all connections are secure.

5. Additional Checks

• If problems persist, conduct a compression test on cylinder 1:
  • Use a compression gauge to check for adequate compression (typically around 150-200 psi).
  • If compression is low, further investigation such as a leak-down test may be required.