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

Solution

1. Preparation

• Gather tools and parts before starting the repair.
• Disconnect the battery to prevent electrical shock.
• Raise the vehicle if necessary and secure it with jack stands.

2. Inspect and Replace Ignition Components

• Sub-steps:
  1. Remove the engine cover if equipped.
  2. Disconnect the electrical connectors from the ignition coils.
  3. Unscrew and remove the ignition coils from the spark plugs.
  4. Remove the spark plugs using a spark plug socket and ratchet.
  5. Inspect the spark plugs for wear, deposits, or damage; replace if necessary.
  6. Install new spark plugs, ensuring the correct gap is set (typically 0.032-0.036 inches for BMW).
  7. Reinstall the ignition coils and reconnect the electrical connectors.

3. Check and Replace Fuel System Components

• Sub-steps:
  1. Test the fuel pressure with a fuel pressure gauge; it should be within the range specified in the service manual (typically around 50-60 psi).
  2. If low, check the fuel filter and replace it if clogged.
  3. Inspect the fuel injectors for proper operation; clean or replace as necessary.
  4. Ensure that there are no leaks in the fuel lines or connections.

4. Inspect Intake and Vacuum Systems

• Sub-steps:
  1. Inspect the air intake duct for cracks or loose connections.
  2. Check the throttle body for carbon buildup; clean if necessary with throttle body cleaner.
  3. Inspect vacuum hoses for breaks or leaks and replace if damaged.