why does my Honda Accord 8th Generation (2008-2012) engine misfire when idling?

Learn how to diagnose and fix engine misfire issues (P0300-P0306) in Honda Accord 8th Generation. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool down before beginning work.

2. Inspect and Replace Spark Plugs

• Tools Required: Socket set, spark plug socket, torque wrench.
• Remove the ignition coil cover by unscrewing any bolts that secure it.
• Disconnect the wiring harness from each ignition coil.
• Use a spark plug socket to carefully remove the spark plugs.
• Inspect the spark plugs for wear; replace them if they are worn or fouled.
• Install new spark plugs and torque them to the manufacturer’s specifications (usually around 13-16 lb-ft).

3. Check and Replace Ignition Coils

• If the spark plugs are in good condition, check the ignition coils.
• Tools Required: Multimeter.
• Use a multimeter to test the primary and secondary resistance of each ignition coil.
• Replace any faulty ignition coils, ensuring to reconnect the wiring harness securely after installation.

4. Clean or Replace Fuel Injectors

• If misfiring persists, inspect the fuel injectors.
• Tools Required: Fuel injector cleaner, cleaning kit (if needed).
• Use a fuel injector cleaner to clean the injectors or replace them if they are clogged.
• Ensure the injector O-rings are intact and replace them if necessary.

5. Inspect for Vacuum Leaks

• Visually inspect all vacuum hoses and the intake manifold for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify any vacuum leaks.
• Repair or replace any damaged hoses or gaskets.

6. Fuel Pressure Test

• Tools Required: Fuel pressure gauge.
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition on (without starting the engine) and check the fuel pressure against manufacturer specifications (usually around 30-50 psi).
• If pressure is low, inspect the fuel pump and fuel filter for issues.