how to diagnose P0302 misfire code on my BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather tools and parts necessary for the repair.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Replace Spark Plug

• Tools Required: Spark plug socket, torque wrench.
• Sub-steps:
  1. Remove the ignition coil from cylinder 2 by unscrewing the retaining bolts and gently lifting it off.
  2. Use the spark plug socket to remove the old spark plug from cylinder 2.
  3. Inspect the new spark plug for the correct gap as per manufacturer specifications.
  4. Install the new spark plug by hand to avoid cross-threading, then tighten it to the manufacturer’s torque specification (usually around 18-20 Nm).

3. Replace Ignition Coil

• Tools Required: Torque wrench, ratchet set.
• Sub-steps:
  1. If the ignition coil was swapped in the diagnostic step, replace it with a new coil if misfire persists.
  2. Remove the old ignition coil and install the new one, ensuring it is seated properly.
  3. Reattach the connector and secure the coil with the retaining bolts, tightening them to the specified torque.

4. Replace Fuel Injector (if necessary)

• Tools Required: Fuel injector puller, torque wrench.
• Sub-steps:
  1. Disconnect the fuel line and electrical connector from the fuel injector in cylinder 2.
  2. Remove the old injector using the injector puller tool.
  3. Lubricate the O-ring of the new injector with engine oil and install it.
  4. Reconnect the fuel line and electrical connection, ensuring a secure fit.

5. Reassemble and Test

• Reconnect the negative battery terminal.
• Clear the trouble codes using the OBD-II scanner.
• Start the engine and monitor for smooth operation.