how to fix P0301 misfire code in my BMW 5 Series G30/G31 (2017-2024)?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, compression tester, socket set, torque wrench, fuel injector cleaner, basic hand tools.
• Disconnect the battery to prevent electrical shorts or shocks.

2. Replace Spark Plug

1. Remove the engine cover if applicable.
2. Disconnect the ignition coil connector for cylinder 1.
3. Unscrew the ignition coil using the appropriate socket.
4. Remove the old spark plug using a spark plug socket.
5. Inspect the spark plug for damage; if worn, replace it with a new spark plug of the same specification (e.g., NGK or Bosch).
6. Apply a small amount of anti-seize compound on the threads of the new spark plug (optional).
7. Torque the new spark plug to the manufacturer’s specification (usually around 20-30 Nm).
8. Reinstall the ignition coil, ensuring it securely connects.

3. Replace Ignition Coil (if necessary)

1. If the ignition coil is damaged or faulty, proceed to replace it.
2. Remove the old ignition coil as described above.
3. Install the new ignition coil, ensuring proper alignment and connection.
4. Reconnect the ignition coil connector.

4. Clean or Replace Fuel Injector (if necessary)

1. If the fuel injector is found to be faulty, remove the fuel rail as per the service manual instructions.
2. Disconnect the fuel line (ensure the fuel system is depressurized).
3. Remove the fuel injector from the rail using pliers or a suitable tool.
4. Clean the injector using a fuel injector cleaner or replace it with a new one if necessary.
5. Reinstall the fuel injector and the fuel rail, ensuring all connections are tight.

5. Perform Compression Test

1. Reconnect the battery and remove the fuel pump fuse to prevent fuel delivery.
2. Insert the compression tester into the spark plug hole for cylinder 1.
3. Crank the engine until the gauge stabilizes and record the reading.
4. Compare the reading against manufacturer specifications (typically around 150-200 psi).

6. Reassemble and Test

1. Reinstall any components removed during the repair.
2. Reconnect the battery.
3. Start the engine and observe for any misfire codes or symptoms.