how to fix P0304 code in 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 necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the ignition coil from cylinder 4.
  1. Unplug the electrical connector from the ignition coil.
  2. Remove the coil mounting bolts and lift the coil out.
• Remove the old spark plug using a spark plug socket.
• Install the new spark plug:
  1. Apply anti-seize lubricant to the spark plug threads (optional).
  2. Hand-tighten the spark plug and then torque to manufacturer specifications (typically around 13 ft-lbs).
• Reinstall the ignition coil, ensuring it is properly seated and connected.

3. Replace Ignition Coil

• If the spark plug replacement does not resolve the issue, proceed to replace the ignition coil.
• Tools Required: Socket set, torque wrench
• Remove the ignition coil from cylinder 4 (as previously detailed).
• Install the new ignition coil:
  1. Position the new coil over the spark plug and push down until seated.
  2. Replace the mounting bolts and tighten to manufacturer specifications.
  3. Reconnect the electrical connector.

4. Check Fuel Injector

• If misfire persists, test or replace the fuel injector for cylinder 4.
• Tools Required: Fuel injector puller, wrench set
• Remove the fuel rail (if necessary) to access the injector.
• Disconnect the fuel line and electrical connector from the injector.
• Remove the old injector and install the new one:
  1. Lubricate the O-ring on the new injector with engine oil.
  2. Insert the new injector and ensure it is properly seated.
  3. Reinstall the fuel rail and reconnect the fuel line.

5. Final Assembly

• Reconnect the negative battery terminal.
• Start the engine and allow it to idle for a few minutes to check for any irregularities.