how to fix P0303 misfire code in BMW 5 Series F10/F11 (2010-2017)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, spark plug socket, fuel injector cleaner, vacuum gauge.
• Ensure the vehicle is parked on a level surface and the engine is cool. Disconnect the battery before starting repairs.

2. Replace Spark Plug

1. Remove the engine cover if applicable.
2. Disconnect the ignition coil connector for cylinder 3.
3. Remove the ignition coil from cylinder 3 using a socket.
4. Use a spark plug socket to remove the spark plug from cylinder 3.
5. Inspect the old spark plug and ensure the new one has the correct gap (refer to manufacturer specifications).
6. Install the new spark plug and torque to the manufacturer’s specifications (usually around 15 ft-lbs).
7. Reinstall the ignition coil and connect the ignition coil connector.

3. Inspect and Replace Ignition Coil

1. If the spark plug replacement does not resolve the issue, remove the ignition coil from cylinder 3.
2. Inspect the ignition coil's electrical connector for damage.
3. Use a multimeter to test the resistance of the ignition coil (please refer to specific resistance values for your model).
4. If the coil fails the test, replace it with a new ignition coil.
5. Reinstall the ignition coil and reconnect the electrical connector.

4. Check Fuel Injector

1. If misfire persists, check the fuel injector for cylinder 3.
2. Remove the fuel injector connector and use a multimeter to check for proper voltage.
3. Perform a flow test or swap the injector with another cylinder to see if the misfire follows.
4. Clean or replace the fuel injector as necessary.
5. Reconnect the fuel injector connector.

5. Vacuum Leak Inspection

1. Inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
2. Use a vacuum gauge to check for manifold pressure and ensure it is within specifications.
3. Address any leaks found by replacing hoses or sealing connections.