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

Solution

1. Preparation

• Gather tools and parts needed.
• Disconnect the battery to ensure safety.
• Use a workspace with sufficient lighting and ventilation.

2. Replace Spark Plugs

• Remove engine cover if applicable.
• Use a spark plug socket and ratchet to remove the spark plugs.
• Inspect the old spark plugs for signs of wear or fouling.
• Install new spark plugs, ensuring the correct gap is set (typically 0.032-0.036 inches for BMW).
• Torque the spark plugs to manufacturer specifications (usually around 18-22 Nm).

3. Inspect and Replace Ignition Coils

• Remove the ignition coil connectors and bolts using a socket set.
• Carefully pull out each ignition coil from the cylinder head.
• Visually inspect the coils for cracks or damage; replace any faulty coils.
• Reinstall the new or verified coils, securing them with bolts and reconnecting the electrical connectors.

4. Check Fuel System

• Attach a fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the "ON" position (without starting the engine) to check if the fuel pressure is within specification (typically around 50-60 psi).
• If the pressure is low, check the fuel pump and fuel filter for clogs or failures, and replace as necessary.

5. Inspect for Vacuum Leaks

• Visually inspect all vacuum lines and the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks; if engine RPM changes, a leak is present.
• Replace any damaged hoses or reseal the intake manifold as necessary.

6. Clean or Replace Fuel Injectors

• If clogged injectors are suspected, use a fuel injector cleaning kit to clean them.
• Alternatively, replace any faulty fuel injectors with OEM replacements.