how to fix engine misfire P0300 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace Spark Plugs

• Sub-steps:
  1. Remove the engine cover (if applicable) by unscrewing any fasteners.
  2. Disconnect the ignition coil connectors.
  3. Remove the ignition coils using a socket set.
  4. Unscrew and remove the old spark plugs using a spark plug socket.
  5. Inspect the old spark plugs for signs of wear or fouling.
  6. Install new spark plugs, ensuring proper gap as per manufacturer specifications (typically 0.043 inches).
  7. Reinstall the ignition coils and their connectors.

3. Test and Replace Ignition Coils (if necessary)

• Sub-steps:
  1. Use a multimeter to test each ignition coil's resistance according to the specifications in the repair manual.
  2. If any coils are out of specification, replace them with new ones.
  3. Reconnect ignition coil connectors and ensure they are seated properly.

4. Inspect Fuel System

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition to the "ON" position (without starting the engine) to check the fuel pressure.
  3. Compare the reading with manufacturer specifications (usually around 50-60 psi).
  4. If pressure is low, inspect the fuel pump, fuel filter, and lines for blockages or damage.

5. Check for Vacuum Leaks

• Sub-steps:
  1. Inspect all vacuum hoses for cracks or disconnections.
  2. Spray a small amount of carburetor cleaner around the intake manifold and vacuum lines while the engine is running. If the idle changes, you have identified a leak.
  3. Repair or replace any damaged hoses or gaskets.