how to fix P0304 misfire in Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool completely before starting work.

2. Inspect and Replace Spark Plug

1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the ignition coil connector on cylinder 4.
3. Remove the ignition coil bolts and gently pull the coil out.
4. Remove the spark plug using a spark plug socket and ratchet.
5. Inspect the spark plug for fouling or wear, and replace with an OEM or equivalent part if necessary.
6. Reinstall the new spark plug and torque to the manufacturer’s specification (usually around 13-16 lb-ft).

3. Check and Replace Ignition Coil

1. If the ignition coil appears damaged, replace it with a new unit.
2. Install the new ignition coil on the spark plug and secure it with bolts.
3. Reconnect the ignition coil connector.

4. Inspect and Replace Fuel Injector (if necessary)

1. If the injector is suspected to be faulty, remove the fuel rail by detaching necessary bolts.
2. Disconnect the fuel injector connector.
3. Remove the old fuel injector from the fuel rail.
4. Install the new fuel injector and reassemble the fuel rail.
5. Reconnect the fuel injector connector and secure the fuel rail.

5. Verify and Reassemble

1. Reattach the engine cover (if removed).
2. Reconnect the negative battery terminal.
3. Start the engine and allow it to idle to check for smooth operation.