how to fix P0302 misfire code on BMW 3 Series E90/E91 (2005-2012)

Solution

1. Preparation

• Ensure the engine is cool before starting work.
• Disconnect the battery to prevent electrical shorts.
• Gather the necessary tools and parts.

2. Replace Spark Plug and Ignition Coil

1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the wiring harness from the ignition coil for cylinder 2.
3. Remove the ignition coil by unscrewing the retaining bolt and pulling it straight out.
4. Remove the spark plug using a spark plug socket and ratchet.
5. Inspect the old spark plug for wear. If it shows signs of wear or fouling, replace it with a new spark plug (ensure proper gap).
6. Install the new spark plug into the cylinder head and torque it to the manufacturer's specification (typically around 18 lb-ft).
7. Insert the new ignition coil into the spark plug hole and secure it with the retaining bolt. Reconnect the wiring harness.

3. Check and Replace Fuel Injector (if necessary)

1. Remove the fuel rail if the injector is not accessible (this may require removing other components).
2. Disconnect the fuel line from the fuel rail using a fuel line disconnect tool.
3. Remove the retaining clips and pull out the fuel injector from the rail.
4. Install the new fuel injector and ensure it is seated properly. Reattach the fuel rail and secure with retaining clips.
5. Reconnect the fuel line and ensure all connections are tight.

4. Clear Codes and Test

1. Reconnect the battery and use the OBD-II scanner to clear the P0302 code.
2. Start the engine and allow it to idle. Check for any abnormal noises or symptoms.
3. Take the vehicle for a test drive to ensure the repair was successful.