how to fix P0304 cylinder 4 misfire in BMW X3 F25 (2011-2018)

Solution

1. Preparation

• Tools Required:
  • OBD-II scanner
  • Socket set
  • Torque wrench
  • Compression tester
  • Multimeter
  • Fuel injector cleaning kit (if needed)
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Replace Spark Plug

• Remove the engine cover (if applicable).
• Disconnect the ignition coil harness for cylinder 4.
• Remove the ignition coil using a socket.
• Remove the spark plug using a spark plug socket.
• Inspect the old spark plug; if it is worn or fouled, replace it with a new spark plug that meets manufacturer specifications.
• Torque the new spark plug to 25 Nm (18.5 lb-ft).
• Reinstall the ignition coil and reconnect the harness.

3. Replace Ignition Coil

• If the ignition coil is faulty, remove it from cylinder 4 following similar steps as above.
• Install a new ignition coil, ensuring it is seated properly.
• Torque the ignition coil mounting bolt to manufacturer specifications.

4. Inspect and Clean Fuel Injector

• If the injector is clogged, remove the fuel rail to access the injector.
• Disconnect the fuel line and electrical connector from the injector.
• Remove the fuel injector from the rail.
• Use a fuel injector cleaning kit to clean the injector or replace it if necessary.
• Reinstall the injector, ensuring it is securely fitted.

5. Compression Test (if misfire persists)

• Remove the spark plug from cylinder 4.
• Insert the compression tester into the spark plug hole.
• Crank the engine to obtain a compression reading.
• Compare the reading to the manufacturer's specifications. A significant deviation may indicate internal engine issues.