how to fix P0300 random misfire code on my Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to avoid electrical shorts.

2. Replace Spark Plugs and Wires

• Tools Required: Socket set, torque wrench, spark plug socket.
• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the spark plug wires from each spark plug.
  3. Using a spark plug socket, carefully remove each spark plug.
  4. Inspect each spark plug for wear and replace with OEM specified spark plugs.
  5. Apply anti-seize compound on the threads of the new spark plugs.
  6. Install new spark plugs by hand, then torque to manufacturer's specifications (typically around 13-15 lb-ft).
  7. Reconnect the spark plug wires ensuring they are seated correctly.

3. Inspect and Replace Ignition Coils

• Tools Required: Socket set, multimeter (for testing).
• Sub-steps:
  1. Disconnect the electrical connectors from the ignition coils.
  2. Remove the ignition coils from the engine by unbolting them.
  3. Test each coil with a multimeter to ensure they are within the specified resistance range.
  4. Replace any faulty coils with OEM replacements.
  5. Reinstall the ignition coils and reconnect the electrical connectors.

4. Check Fuel System

• Tools Required: Fuel pressure gauge.
• Sub-steps:
  1. Locate the fuel rail and connect the fuel pressure gauge.
  2. Turn the ignition on (do not start the engine) and check the fuel pressure; compare with manufacturer specifications.
  3. If pressure is low, inspect the fuel pump and filter for blockages or failures.
  4. Replace the fuel filter if necessary and ensure the fuel pump is functioning correctly.

5. Inspect Air Intake and Vacuum System

• Tools Required: Screwdrivers, vacuum gauge.
• Sub-steps:
  1. Remove the air intake duct and clean or replace the air filter if necessary.
  2. Inspect the intake manifold for leaks or cracks.
  3. Use a vacuum gauge to check for any vacuum leaks; repair any leaks found.
  4. Reassemble the air intake system ensuring all connections are secure.