how to fix P0304 misfire code on Honda Accord 8th Generation (2008-2012)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Honda Accord 2008-2012. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the engine is cool and disconnect the negative battery terminal to prevent electrical shock.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, gap gauge
• Remove the ignition coil for cylinder 4:
  • Disconnect the electrical connector from the ignition coil.
  • Remove the bolt securing the ignition coil and lift it out.
• Remove the spark plug:
  • Use a spark plug socket to unscrew the spark plug from cylinder 4.
  • Inspect the spark plug for wear and replace if necessary.
• Install the new spark plug:
  • Ensure the spark plug gap is set to the manufacturer’s specifications (typically 0.043 inches for Honda).
  • Torque the spark plug to the manufacturer’s specification (usually 13 lb-ft).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Inspect and Replace Ignition Coil

• If the spark plug is fine, test the ignition coil:
  • Use a multimeter to check the coil’s resistance (primary and secondary).
  • Replace the ignition coil if it fails the test.
• Install the new ignition coil and make sure it is seated properly.

4. Check Fuel Injector

• If issues persist, inspect the fuel injector:
  • Remove the fuel rail to access the injector for cylinder 4.
  • Use a noid light to check for proper electrical signal; replace the injector if it’s not functioning.
• Reinstall the fuel rail and ensure all connections are secure.

5. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0304 code.
• Start the engine and let it idle for a few minutes before taking it for a test drive to monitor for any recurrence of the misfire.