how to fix P0304 misfire code in 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

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on it.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil from cylinder 4 by unscrewing the bolts and disconnecting the electrical connector.
• Use a spark plug socket to remove the old spark plug from cylinder 4.
• Inspect the old spark plug for signs of wear; replace it if necessary with a new one that meets OEM specifications (usually around 0.044 inches gap).
• Install the new spark plug by hand to avoid cross-threading, then torque to the manufacturer's specification (typically around 13 lb-ft).

3. Replace Ignition Coil

• Tools Required: Socket set, torque wrench.
• After removing the ignition coil, inspect the connector for corrosion.
• Install the new ignition coil onto the spark plug and secure it with bolts; torque to manufacturer specifications (usually around 8 lb-ft).
• Reconnect the electrical connector to the ignition coil.

4. Inspect and Clean Fuel Injector

• Tools Required: Fuel injector cleaning kit (if needed), multimeter.
• Disconnect the electrical connector from the fuel injector for cylinder 4.
• Use a multimeter to test the injector’s resistance; replace if out of specification.
• Clean the injector using a fuel injector cleaning kit or replace it with a new one if necessary.

5. Compression Test

• Tools Required: Compression gauge.
• Reconnect the ignition coil and spark plug temporarily.
• Remove the fuel pump fuse to prevent fuel delivery.
• Crank the engine and take the compression reading.
• If compression is low, further investigation into valve issues or head gasket failure may be required.