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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is off.
• Disconnect the battery to ensure safety.

2. Replace Spark Plug and Ignition Coil (if necessary)

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover if applicable.
• Disconnect the electrical connector from the ignition coil for cylinder 2.
• Unbolt the ignition coil and remove it from the cylinder head.
• Remove the spark plug using a spark plug socket and inspect it for wear or damage.
• Install a new spark plug, torque to manufacturer specifications (typically 18-22 Nm).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Check and Replace Fuel Injector (if necessary)

• Tools Required: Fuel line disconnect tool, injector puller (if needed).
• Relieve fuel pressure by removing the fuel pump fuse and starting the engine until it stalls.
• Disconnect the fuel injector connector for cylinder 2.
• Use a fuel line disconnect tool to remove the fuel line from the injector.
• Unbolt the fuel injector and remove it from the intake manifold.
• Install the new fuel injector, ensuring proper O-ring placement and securing it in place.
• Reconnect the fuel line and electrical connector.

4. Conduct Compression Test (if necessary)

• Tools Required: Compression gauge.
• Ensure all spark plugs are removed.
• Insert the compression gauge into the spark plug hole of cylinder 2.
• Crank the engine several times to obtain a reading.
• Compare the reading to manufacturer specifications. If low, further inspection may be required.