what causes the P0301 misfire code in my BMW 3 Series G20/G21 (2019-2024)?

Solution

1. Preparation

• Gather necessary tools and parts before starting the repair.
• Disconnect the vehicle's battery to avoid electrical hazards.
• Ensure the engine is cool before working on ignition components.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, gap gauge
• Remove the engine cover (if applicable) to access the spark plug.
• Use the socket wrench to remove the spark plug from cylinder 1.
• Inspect the old spark plug for signs of wear (e.g., carbon buildup, worn electrode).
• Install a new spark plug, ensuring it is gapped to manufacturer specifications (typically around 0.030 to 0.040 inches).
• Torque the new spark plug to the manufacturer's specifications (usually around 18-25 Nm).

3. Replace Ignition Coil

• Tools Required: Socket set
• Disconnect the connector from the ignition coil for cylinder 1.
• Remove the bolt securing the ignition coil and lift it out.
• Install the new ignition coil, securing it with the bolt and reconnecting the connector.

4. Check Fuel Injector

• Tools Required: Fuel injector cleaning kit (if cleaning), or replacement injector
• Disconnect the fuel injector connector on cylinder 1.
• Remove the fuel rail if necessary to access the injector.
• Inspect the injector for clogs; clean it if possible or replace with a new injector as necessary.
• Reinstall the injector and reconnect the fuel rail and electrical connectors.

5. Perform Compression Test

• Tools Required: Compression tester
• Remove the spark plug from cylinder 1.
• Screw in the compression tester and crank the engine to measure the compression.
• Compare the reading against the manufacturer’s specifications (typically around 150-200 psi).
• If compression is low, further investigation of piston rings, valves, or head gasket may be needed.