how to fix P0300 code misfire in Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather required tools and parts.
• Disconnect the negative battery terminal.
• Allow the engine to cool down completely before starting work.

2. Replace Spark Plugs

• Remove the ignition coils by unscrewing them and gently pulling them off the spark plugs.
• Use a spark plug socket to remove the old spark plugs. Ensure you use the proper torque (typically 13-16 lb-ft for Toyota spark plugs) when installing new ones.
• Install the new spark plugs and reconnect the ignition coils.

3. Check and Replace Ignition Coils (if necessary)

• If any ignition coils were found to be faulty during diagnostics, remove them by unscrewing the mounting bolts.
• Disconnect the electrical connector from each ignition coil.
• Replace with new ignition coils, ensuring they are compatible with the vehicle.
• Reconnect the electrical connectors and secure them with the bolts.

4. Inspect Fuel Injectors

• Remove the fuel rail if necessary (ensure fuel system is depressurized before disconnecting hoses).
• Check the injectors for proper function; replace any that are leaking or not delivering fuel correctly.
• Clean the fuel injectors using a fuel injector cleaning kit if they appear clogged.

5. Check for Vacuum Leaks

• Inspect all vacuum lines for cracks or disconnections. Replace any damaged hoses.
• Use a smoke machine or carburetor cleaner to detect leaks around the intake manifold and vacuum lines.

6. Fuel Pressure Test

• Connect a fuel pressure gauge to the fuel rail's test port.
• Turn the ignition to the "ON" position without starting the engine and check the pressure reading. Ensure it matches the manufacturer’s specifications (typically around 43-50 psi for a Corolla).
• If the pressure is low, investigate the fuel pump and fuel filter for potential issues.