how to fix P0304 misfire code in Tesla Outback 4th Generation (2010-2014)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Subaru Outback (2010-2014). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather all 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 short circuits.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, spark plug socket, torque wrench
• Remove the ignition coil from cylinder 4:
  1. Disconnect the electrical connector from the ignition coil.
  2. Unscrew the bolts securing the coil and carefully pull it out.
• Remove the spark plug using a spark plug socket:
  1. Turn counterclockwise to loosen and remove the spark plug.
• Inspect the spark plug for fouling or wear. Replace if necessary with the manufacturer-recommended spark plug (e.g., NGK, Denso).
• Torque the new spark plug to the specified value (typically around 13 lb-ft).

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, inspect the ignition coil:
  1. Visually check for cracks, carbon tracking, or other signs of failure.
  2. If defective, replace it with an OEM or quality aftermarket ignition coil designed for the Outback.
• Reinstall the ignition coil:
  1. Position the coil over the spark plug and secure it with the bolts.
  2. Reconnect the electrical connector.

4. Check Fuel Injector

• If the misfire persists, check the fuel injector for cylinder 4:
  1. Use a multimeter to test the injector resistance; it should match manufacturer specifications.
  2. If faulty, replace the fuel injector.
• Reconnect the fuel rail and any electrical connectors.

5. Reassembly and Final Checks

• Reconnect the negative battery terminal.
• Ensure all components are securely installed and any tools are removed from the engine bay.