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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, compression tester, torque wrench.
• Disconnect the battery to ensure safety while working on electrical components.

2. Replace Spark Plugs

1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the ignition coils by unclipping the wiring harness.
3. Remove the ignition coils by unscrewing them from the engine.
4. Remove the old spark plugs using a spark plug socket.
5. Install new spark plugs, ensuring the correct gap (typically 0.032-0.036 inches) is set.
6. Reinstall the ignition coils and connect the wiring harness.

3. Replace Ignition Coils

1. If misfire persists, remove the ignition coils as described above.
2. Install new ignition coils, ensuring they are seated properly.
3. Reconnect the wiring harness to each coil.

4. Inspect and Clean Fuel Injectors

1. Remove fuel injector connectors and unscrew the injectors from the fuel rail.
2. Clean the injectors using a specialized cleaning solution or replace them if necessary.
3. Reinstall the injectors and reconnect the fuel rail.

5. Check for Vacuum Leaks

1. Inspect all vacuum lines for cracks or disconnections; replace any damaged hoses.
2. Use a smoke machine to detect leaks if needed.

6. Perform a Compression Test

1. Remove the spark plugs.
2. Insert the compression tester into the spark plug hole of the suspected cylinders.
3. Crank the engine and note the compression readings; compare with manufacturer specifications (usually around 150-200 psi).
4. Address any low compression findings, which may indicate further engine issues.