how to fix the P0303 misfire code on BMW X3 G01 (2018-2024)

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 prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the engine cover if applicable.
• Disconnect the ignition coil connector on cylinder 3.
• Remove the ignition coil using the socket set.
• Unscrew the spark plug using the spark plug socket.
• Inspect the spark plug for wear, carbon deposits, or damage.
• If necessary, replace the spark plug with a new one, ensuring it is gapped correctly as per manufacturer specifications (typically around 0.032-0.036 inches).
• Reinstall the ignition coil and connector, ensuring it is seated correctly.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, proceed to the ignition coil.
• Remove the ignition coil from cylinder 3 as described above.
• Test the ignition coil with a multimeter to ensure it is within specified resistance values (refer to the vehicle service manual).
• If it fails the test, replace the ignition coil with a new one.
• Reinstall the ignition coil and reconnect the wiring harness.

4. Check and Clean Fuel Injector

• Remove the fuel injector from cylinder 3.
• Inspect for clogs or carbon buildup.
• Clean the injector using a fuel injector cleaner or replace it if necessary.
• Reinstall the fuel injector, ensuring proper sealing and connections.

5. Conduct Compression Test

• If misfire persists, perform a compression test on cylinder 3.
• Insert the compression gauge into the spark plug hole.
• Crank the engine and record the compression reading.
• Compare with specifications (usually 120-200 psi depending on the engine).
• If readings are low, further investigation into valve seating or piston rings may be necessary.