how to fix the P0304 misfire code in my Toyota Corolla E170 (2013-2019)

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 tools and parts needed for repair.
• Disconnect the negative battery terminal to prevent electrical shock.
• Allow the engine to cool before starting work.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the ignition coil from cylinder 4 by unscrewing the mounting bolts and disconnecting the electrical connector.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for fouling or wear. If necessary, replace it with a new spark plug that meets OEM specifications.
• Reinstall the spark plug, tightening it to the manufacturer's torque specification (typically around 13 lb-ft or as specified in the service manual).
• Reattach the ignition coil and connector.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, test the ignition coil for proper function using a multimeter.
• If faulty, remove the ignition coil and replace it with a new one that matches OEM specifications.
• Reinstall the new ignition coil and reconnect the electrical connector.

4. Inspect and Clean Fuel Injector

• Remove the fuel injector from cylinder 4.
• Use a fuel injector cleaner to clean the injector or replace it if it is clogged or malfunctioning.
• Reinstall the fuel injector and ensure it is properly seated.

5. Check and Repair Vacuum Leaks

• Inspect all vacuum hoses and the intake manifold gasket for leaks.
• Replace any damaged hoses or gaskets as necessary.

6. Final Checks

• Reconnect the battery terminal.
• Clear the error codes using the OBD-II scanner.
• Start the engine and allow it to reach operating temperature.