how to fix P0304 code in Honda Accord Eleventh Generation (2023-present)

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

Solution

1. Preparation

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

2. Replace Spark Plug and Ignition Coil

• Tools Required: Socket set, torque wrench, spark plug socket, ratchet, dielectric grease.
• Remove the engine cover (if applicable) by unscrewing the bolts.
• Locate the ignition coil for cylinder 4 (usually marked or indicated in the service manual).
• Disconnect the electrical connector from the ignition coil.
• Remove the ignition coil by unscrewing it from the cylinder head.
• Remove the spark plug using the spark plug socket and ratchet; inspect for wear or damage.
• Install the new spark plug, torqueing it to the manufacturer's specification (typically around 13 lb-ft).
• Apply dielectric grease to the ignition coil connector and re-install the ignition coil, ensuring it is securely fastened.

3. Inspect and Clean Fuel Injector

• Tools Required: Fuel injector cleaner (if necessary), fuel pressure gauge.
• Disconnect the fuel injector connector for cylinder 4.
• Remove the fuel injector from the fuel rail (ensure to relieve fuel pressure before this step).
• Clean the injector using fuel injector cleaner or replace it with a new one if necessary.
• Reinstall the injector, ensuring it is secured properly and reconnect the electrical connector.

4. Compression Test (if misfire persists)

• Tools Required: Compression gauge.
• Remove the spark plug from cylinder 4 again.
• Insert the compression gauge into the spark plug hole.
• Crank the engine and record the compression reading; it should match the manufacturer's specifications (typically around 180-200 psi).
• If compression is low, further investigation into engine internals may be needed (e.g., valve issues, piston rings).