why is my Toyota Corolla E140 (2006-2013) throwing a P0303 code

Learn how to diagnose and fix P0303 cylinder 3 misfire in Toyota Corolla. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

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

2. Inspect and Replace Ignition Components

1. Remove Ignition Coil
   • Unscrew the mounting bolt securing the ignition coil on cylinder 3.
   • Carefully disconnect the electrical connector and lift the coil out.
2. Check Spark Plug
   • Remove the spark plug from cylinder 3 using a spark plug socket.
   • Inspect for wear, carbon buildup, or damage. Replace if necessary.
3. Install New Components
   • Install a new spark plug, ensuring it is gapped correctly per manufacturer specifications (typically 0.044 inches).
   • Reattach the ignition coil, ensuring the electrical connector clicks into place and secure with the mounting bolt.

3. Inspect and Clean Fuel Injector

1. Remove Fuel Injector
   • Relieve fuel system pressure by removing the fuel pump fuse and running the engine until it stalls.
   • Disconnect fuel lines and electrical connectors from the injector.
   • Remove the fuel injector from cylinder 3.
2. Clean or Replace Injector
   • Clean the injector using a specialized cleaning kit or replace it with a new one.
   • Reinstall the injector and reconnect fuel lines and electrical connectors.

4. Compression Test

1. Perform Compression Test
   • Remove the spark plug from cylinder 3 and install the compression gauge.
   • Crank the engine and record the compression reading. Compare it to the manufacturer's specifications (typically 180-220 psi).
   • If low, further investigation may be needed for internal engine issues.

5. Check for Vacuum Leaks

1. Inspect Hoses and Manifold
   • Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
   • Use carburetor cleaner or a smoke machine to identify any leaks.
   • Repair or replace any damaged components as necessary.