how to fix P0304 misfire code on my 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

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, spark plug socket, fuel injector cleaner.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil for cylinder 4 using the socket set.
• Extract the spark plug using the spark plug socket.
  • Sub-steps:
    • Inspect the spark plug for wear, carbon buildup, or damage.
    • If faulty, replace with a new spark plug (Toyota OEM recommended).
    • Torque the new spark plug to the manufacturer’s specification (typically 13 lb-ft).
• Reinstall the ignition coil ensuring it is seated properly.

3. Test and Replace Ignition Coil

• Use a multimeter to test the ignition coil's resistance according to the specifications.
  • Sub-steps:
    • If the ignition coil is faulty, replace it with a new one.
    • Reconnect the ignition coil securely.

4. Inspect and Clean Fuel Injector

• Disconnect the fuel injector connector for cylinder 4.
• Remove the fuel injector using the appropriate tools.
  • Sub-steps:
    • Clean the injector with fuel injector cleaner or replace if damaged.
    • Reinstall the injector ensuring it is seated properly.
    • Reconnect the injector connector.

5. Compression Test (if necessary)

• Conduct a compression test on cylinder 4 to check for mechanical failure.
  • Sub-steps:
    • If compression is low, inspect for valve issues or head gasket failure.
    • Address any mechanical issues as necessary.