how to diagnose engine misfire in BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, compression tester, fuel injector cleaning kit.
• Disconnect the negative battery terminal to ensure safety while working on the engine.
• Allow the engine to cool completely before beginning any work.

2. Replace Spark Plugs

• Remove the engine cover (if applicable) and access the spark plugs.
• Using a spark plug socket, carefully remove the spark plugs one at a time.
• Inspect the old spark plugs for signs of wear or damage.
• Install new spark plugs with the correct gap as per manufacturer specifications (typically around 0.030 inches).
• Torque the spark plugs to the manufacturer's recommended specification (usually around 15-20 Nm).

3. Test and Replace Ignition Coils

• Disconnect the electrical connector from the ignition coil.
• Remove the ignition coil from the cylinder head using a socket.
• Test the ignition coil with a multimeter (check resistance according to specifications).
• Replace any faulty ignition coils with new units.
• Reinstall the ignition coils and reconnect the electrical connectors.

4. Inspect and Clean Fuel Injectors

• Remove the fuel rail to access the fuel injectors (ensure to relieve fuel pressure first).
• Inspect each injector for clogs or leaks.
• Use a fuel injector cleaning kit to clean the injectors, or replace them if necessary.
• Reinstall the fuel rail and ensure all connections are secure.

5. Check for Vacuum Leaks

• Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use a smoke machine to detect any vacuum leaks if necessary.
• Replace any damaged hoses or reattach loose connections.

6. Perform Compression Test

• Remove all spark plugs to facilitate access and prevent engine damage.
• Insert the compression tester into each cylinder and crank the engine to take readings.
• Compare the compression readings against the manufacturer’s specifications to identify any issues.
• Address any low compression readings by investigating potential causes (e.g., valve or piston issues).