how to fix a misfire on my Toyota Highlander XU70 (2020-Present) that throws a P0300 code?

Solution

1. Preparation

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

2. Replace Spark Plugs

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the engine cover if necessary to access the spark plugs.
• Use the spark plug socket to remove old spark plugs.
• Inspect the old plugs for signs of wear or fouling.
• Install new spark plugs to the manufacturer's specifications (usually 13-15 ft-lbs torque).
• Reattach the engine cover if it was removed.

3. Check and Replace Ignition Coils

• Tools Required: Socket set, torque wrench, multimeter
• Disconnect the electrical connector from each ignition coil.
• Remove the ignition coils using the socket set.
• Use the multimeter to test each coil for resistance; compare with specifications in the repair manual.
• Replace any faulty ignition coils with new ones.
• Reinstall the ignition coils and reconnect the electrical connectors.

4. Inspect and Clean Fuel Injectors

• Tools Required: Fuel injector cleaning kit, safety goggles, gloves
• Disconnect the fuel injector electrical connectors.
• Remove the fuel rail to access the injectors.
• Inspect injectors for clogs; clean using a fuel injector cleaning kit if applicable.
• Reinstall the injectors and reconnect electrical connectors.

5. Check Vacuum Hoses

• Inspect all vacuum hoses in the engine bay for cracks or disconnections.
• Replace any damaged hoses with new ones to ensure proper vacuum levels.

6. Test Fuel Pressure

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the "ON" position (do not start the engine) to check for initial pressure.
• Start the engine and observe the fuel pressure reading; ensure it matches manufacturer specifications.
• If the pressure is low, consider replacing the fuel pump or fuel filter.