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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety.
• Allow the engine to cool down before starting work.

2. Replace Spark Plugs

• Remove the ignition coil cover to access the spark plugs.
• Using a socket wrench, remove the spark plugs from each cylinder.
• Inspect the old spark plugs for signs of wear. If damaged, replace with new OEM spark plugs.
• Torque the new spark plugs to the manufacturer’s specifications (typically around 22 Nm or 16 lb-ft).
• Reinstall the ignition coils and ensure they are seated correctly.

3. Inspect and Replace Ignition Coils (if necessary)

• If any ignition coils were found to be faulty during diagnostics, remove them by unscrewing the retaining bolts.
• Disconnect the electrical connector from the ignition coil.
• Install new ignition coils by reversing the removal steps. Ensure they are securely attached and connected.

4. Fuel System Check

• Connect a fuel pressure gauge to the fuel rail to check fuel pressure against manufacturer specifications.
• If pressure is low, inspect the fuel filter and fuel pump; replace as necessary.
• Clean or replace any clogged fuel injectors using an injector cleaning solution or ultrasonic cleaner.

5. Vacuum Leak Inspection

• Inspect all vacuum hoses for cracks or disconnections.
• Check the intake manifold for leaks using a smoke machine or by spraying carburetor cleaner around the seams and listening for changes in engine RPM.
• Repair or replace any damaged hoses or gaskets identified during the inspection.