how to fix P0300 misfire code in BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.

2. Inspect Ignition Components

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover if applicable.
• Remove ignition coils from the cylinders by unscrewing bolts or clips.
• Inspect the spark plugs for fouling or wear. Replace if needed (use OEM specifications).
• Reinstall the ignition coils and torque to specifications (typically around 10 Nm).

3. Check for Vacuum Leaks

• Tools Required: Smoke machine or carburetor cleaner.
• With the engine running, apply smoke or carburetor cleaner around intake manifold gaskets and vacuum hoses.
• Look for changes in engine RPM to identify leaks.
• Replace any damaged hoses or gaskets found during inspection.

4. Verify Fuel System

• Tools Required: Fuel pressure gauge.
• Locate the fuel rail and connect the fuel pressure gauge.
• Turn the ignition to the "ON" position (do not start the engine) to check the fuel pump pressure.
• Compare the reading with manufacturer specifications (usually around 50-60 psi).
• Replace the fuel filter if pressure is low, and check the fuel injectors for clogs.

5. Perform Compression Test

• Tools Required: Compression tester.
• Remove spark plugs and install the compression tester in each cylinder.
• Crank the engine and note the pressure reading.
• Compare readings against manufacturer specifications (generally around 140-200 psi).
• If compression is low in any cylinder, further inspection of the piston rings or valves may be necessary.

6. Reassemble and Test

• Reinstall all components in reverse order.
• Reconnect the battery and clear the error codes using the OBD-II scanner.
• Start the engine and check for any new codes or symptoms.