how to fix P0302 misfire code in BMW 3 Series E90/E91 (2005-2012)?

Solution

1. Preparation

• Gather tools and parts required.
• Ensure the vehicle is parked on a level surface with the engine off.
• Disconnect the battery negative terminal to prevent electrical shorts.

2. Replace Spark Plug

• Remove the engine cover if applicable.
• Locate cylinder 2 (usually the second cylinder from the front of the engine).
• Use a spark plug socket and ratchet to remove the old spark plug.
• Inspect the spark plug for signs of fouling or wear.
• Install a new spark plug (manufacturer recommended type) and torque to the specified value (typically around 18 lb-ft).

3. Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil on cylinder 2.
• Remove the retaining bolt(s) securing the ignition coil.
• Pull the ignition coil straight out from the spark plug.
• Install the new ignition coil and secure it with the retaining bolt(s).
• Reconnect the electrical connector.

4. Test/Replace Fuel Injector

• Disconnect the fuel injector connector for cylinder 2.
• To test, use a noid light connected to the injector connector to check for signal.
• If there is no signal, further diagnosis is required on the engine control unit (ECU).
• If replacing, remove the fuel rail if necessary, then unclip and replace the injector.
• Reinstall the fuel rail and reconnect all necessary connectors.

5. Check for Vacuum Leaks

• Inspect all vacuum hoses connected to the intake manifold.
• Use a smoke machine or carburetor cleaner to detect leaks while the engine is idling.
• Repair or replace any damaged hoses or gaskets found.