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

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, multimeter, compression gauge, fuel pressure gauge, and vacuum gauge.
• Ensure the vehicle is parked on a level surface and secure the vehicle with wheel chocks.

2. Replace Spark Plugs

• Remove the ignition coil covers (if applicable) using a socket set.
• Disconnect the electrical connectors from the ignition coils.
• Unscrew and remove the ignition coils.
• Use a spark plug socket to unscrew the old spark plugs.
• Inspect the new spark plugs for proper gap and install them into the cylinder head.
• Reinstall the ignition coils and reconnect the electrical connectors.

3. Inspect and Replace Ignition Coils

• If any ignition coils were found faulty, remove them as described above.
• Install new ignition coils in the same order, ensuring they seat properly.
• Reconnect electrical connectors.

4. Fuel Injector Inspection

• Disconnect fuel injector connectors.
• Use a multimeter to check the resistance of each injector (consult specifications for correct values).
• If faulty, replace the fuel injectors.
• Reconnect all connectors after inspection.

5. Compression Testing

• Remove spark plugs.
• Insert the compression gauge into the spark plug hole of each cylinder.
• Crank the engine and record the pressure. Compare it against manufacturer specifications.
• If compression is low, it may indicate a need for further internal engine diagnostics.

6. Vacuum Leak Testing

• Attach a vacuum gauge to a manifold vacuum port.
• Start the engine and observe the gauge. A steady reading indicates no leaks; fluctuations may point to vacuum leaks.
• If leaks are found, replace the affected hoses or gaskets.