how to fix P0303 misfire code in BMW X3 G01 (2018-2024)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool before beginning work to prevent burns.

2. Replace Spark Plug

• Tools Required: Socket set, spark plug socket, torque wrench
• Remove the engine cover if necessary.
• Disconnect the ignition coil connector for cylinder 3.
• Remove the ignition coil by unscrewing the retaining bolts and lifting it out.
• Unscrew the spark plug using a spark plug socket.
• Inspect the old spark plug for wear; replace it with a new spark plug, ensuring it is gapped to manufacturer specifications (typically around 0.030-0.035 inches).
• Torque the spark plug to the specified value (usually about 15-20 Nm).
• Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if necessary)

• If the ignition coil was found defective during diagnostics:
• Tools Required: Socket set
• Remove the faulty ignition coil as described in the previous step.
• Install the new ignition coil, ensuring it fits securely.
• Reconnect the ignition coil connector.

4. Inspect and Clean Fuel Injector (if necessary)

• If the fuel injector is suspected to be malfunctioning:
• Tools Required: Fuel injector puller, cleaning solvent, O-rings
• Relieve fuel system pressure by removing the fuel pump fuse and starting the engine until it stalls.
• Disconnect the fuel injector connector and remove the injector using the fuel injector puller.
• Clean the injector with a suitable cleaning solvent and replace the O-rings before reinstalling.

5. Compression Test (if necessary)

• If compression issues are suspected:
• Tools Required: Compression tester
• Remove the spark plug from cylinder 3.
• Insert the compression tester into the spark plug hole.
• Crank the engine and record the compression reading.
• Compare the result with the manufacturer's specifications (usually around 140-200 psi depending on the engine).
• If the compression is low, further investigation is needed for potential internal engine problems.