how to fix P0300 misfire code in BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Spark Plugs

• Remove the engine cover if necessary to access the spark plugs.
• Use a spark plug socket and ratchet to remove each spark plug.
• Inspect the spark plugs for wear, carbon deposits, or damage.
• Replace with OEM spark plugs, ensuring the gap is set to manufacturer specifications (typically 0.025-0.030 inches).
• Install new spark plugs and torque to the manufacturer’s specifications (around 15 ft-lbs).

3. Check and Replace Ignition Coils

• Remove the ignition coils by disconnecting the electrical connectors and unscrewing the bolts.
• Inspect each coil for cracks or damage.
• If faulty, replace with OEM ignition coils.
• Reinstall coils and ensure connectors are securely attached.

4. Fuel System Check

• Connect a fuel pressure gauge to the fuel rail Schrader valve.
• Turn the ignition to the "ON" position (without starting the engine) and check the fuel pressure; it should match the specifications (typically around 50-60 psi).
• If pressure is low, inspect the fuel pump, fuel filter, and fuel injectors for any blockage or failure.

5. Vacuum Leak Inspection

• Visually inspect all vacuum hoses for cracks or disconnections.
• Use a smoke machine to detect vacuum leaks if necessary.
• Replace any damaged hoses to restore proper vacuum pressure.

6. Compression Test

• Remove the spark plugs to facilitate the test.
• Insert a compression tester into each cylinder and crank the engine.
• Record the compression readings; they should be within manufacturer specifications (typically 150-200 psi).
• If readings are low, further investigation into the engine internals may be required.