how to fix P0304 misfire code in Toyota Corolla E140 (2006-2013)

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

Solution

1. Preparation

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

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug gap tool
• Remove the engine cover if applicable.
• Disconnect the ignition coil connector for cylinder 4.
• Remove the ignition coil using a socket.
• Unscrew and remove the spark plug using the socket.
• Install a new spark plug, ensuring it is gapped according to specifications (typically 0.044 inches for Corolla).
• Torque the spark plug to the manufacturer's specification (usually around 13 lb-ft).
• Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if necessary)

• If the ignition coil was found faulty during diagnostics, replace it.
• Tools Required: Socket set
• Remove the faulty ignition coil as described in the previous step.
• Install the new ignition coil and reconnect the wiring harness.

4. Clean or Replace Fuel Injector (if necessary)

• If the fuel injector is clogged, either clean it or replace it.
• Tools Required: Fuel injector cleaning kit or replacement injector
• Remove the fuel rail according to shop manual instructions.
• Disconnect the fuel injector connectors and remove the injectors.
• Clean the injector using a cleaning kit or replace with a new injector.
• Reinstall the injectors, ensuring proper seating, and reconnect the fuel rail.

5. Reassemble and Reconnect

• Reinstall any components removed during the process.
• Reconnect the negative battery terminal.
• Start the engine and check for smooth operation.