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

Solution

1. Preparation

• Gather required tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coil covers (if applicable).
  2. Disconnect the ignition coils from the spark plugs.
  3. Remove the old spark plugs using a spark plug socket.
  4. Install new spark plugs, ensuring they are gapped correctly (refer to OEM specifications).
  5. Reconnect the ignition coils and covers.

3. Inspect and Replace Ignition Coils (if necessary)

• Sub-steps:
  1. Remove the ignition coils as described in the previous step.
  2. Test each coil with a multimeter to check for resistance (refer to specific resistance values for your model).
  3. Replace any faulty ignition coils with OEM parts.
  4. Reinstall the ignition coils securely.

4. Check and Clean Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the fuel injectors.
  2. Inspect the injectors for clogs and leaks.
  3. Clean the injectors using a fuel injector cleaning kit or replace them if damaged.
  4. Reassemble the fuel rail and ensure all connections are secure.

5. Test Fuel Pressure

• Sub-steps:
  1. Attach a fuel pressure gauge to the fuel rail.
  2. Turn the ignition on (do not start the engine) to check for baseline pressure.
  3. Compare readings with manufacturer specifications.
  4. If the pressure is low, investigate the fuel pump and filter.

6. Inspect Vacuum Lines

• Sub-steps:
  1. Visually inspect all vacuum lines for cracks or disconnections.
  2. Replace any damaged vacuum lines with OEM replacements.
  3. Recheck the engine for any changes in performance.