how to fix P0300 misfire code in BMW 3 Series G20/G21 (2019-2024)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on it.

2. Inspect and Replace Spark Plugs

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover if applicable.
• Disconnect the ignition coils from the spark plugs.
• Use a spark plug socket to carefully remove each spark plug.
• Inspect the spark plugs for wear; replace with OEM parts if damaged or fouled.
• Torque new spark plugs to manufacturer specifications (typically around 20 Nm).
• Reconnect the ignition coils.

3. Check and Replace Ignition Coils

• Tools Required: Socket set, torque wrench.
• Remove the ignition coils (if not previously done).
• Inspect each coil for cracks or signs of wear; replace any faulty coils with OEM parts.
• Reinstall ignition coils and torque to manufacturer specifications.

4. Clean or Replace Fuel Injectors

• Tools Required: Fuel injector cleaning kit or replacement injectors.
• Disconnect the fuel rail and remove injectors.
• If cleaning, follow the injector cleaning kit instructions; if replacing, install new injectors.
• Reassemble the fuel rail and reconnect all lines.

5. Perform a Compression Test

• Tools Required: Compression tester kit.
• Remove the spark plugs again for access.
• Insert the compression tester into the spark plug hole and crank the engine.
• Record the pressure readings for each cylinder; compare with manufacturer specifications.
• If compression is low in any cylinder, further investigation may be needed (e.g., valve or head gasket issues).