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, ensuring safety before working on electrical components.

2. Inspect and Replace Spark Plugs

• Remove the engine cover (if applicable).
• Use a spark plug socket to carefully remove the spark plugs.
• Inspect each spark plug for wear or damage; replace any that are fouled or worn.
• Install new spark plugs, ensuring they are gapped correctly according to manufacturer specifications (typically around 0.028 - 0.032 inches).
• Torque the spark plugs to the manufacturer’s specification (usually around 15-20 ft-lbs).

3. Check and Replace Ignition Coils

• Disconnect the electrical connector from each ignition coil.
• Remove the bolts holding the ignition coils and carefully pull them out.
• Inspect the coils for cracks or damage; replace any faulty coils with new ones.
• Reinstall the ignition coils and reconnect the electrical connectors, ensuring a secure fit.

4. Inspect Fuel System

• Use a fuel pressure gauge to check fuel pressure at the fuel rail; it should match specifications (typically around 50-60 psi).
• If pressure is low, check the fuel pump and fuel filter for blockages or failures.
• Replace the fuel filter if clogged, and consider replacing the fuel pump if it fails to deliver proper pressure.

5. Check for Vacuum Leaks

• Visually inspect hoses and connections for cracks or disconnections.
• Use carburetor cleaner or a smoke machine to detect leaks around intake gaskets, vacuum hoses, and throttle body.
• Repair or replace any damaged components found during inspection.

6. Clean or Replace MAF Sensor

• Disconnect the MAF sensor electrical connector and remove the sensor from the intake duct.
• Clean the MAF sensor using MAF cleaner spray; do not use other cleaners as they may damage the sensor.
• Reinstall the sensor and reconnect the electrical connector.