how to fix P0300 random misfire code on my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Replace Spark Plugs

• Tools Required: Spark plug socket, torque wrench, ratchet, extension.
• Remove the engine cover if applicable.
• Use a spark plug socket to remove the spark plugs.
• Inspect the spark plugs for wear, carbon buildup, or damage.
• Replace with OEM or recommended spark plugs, ensuring to torque them to the manufacturer’s specifications (typically around 13-16 lb-ft).

3. Check and Replace Ignition Coils

• Tools Required: Ratchet, socket set, torque wrench.
• Remove the ignition coils by unscrewing the bolts securing them to the engine.
• Inspect the ignition coils for cracks or carbon tracking.
• Replace any faulty coils with new units (ensure they are compatible with the Highlander model).
• Torque the ignition coil bolts to the specified value (usually around 8-10 lb-ft).

4. Fuel System Inspection

• Tools Required: Fuel pressure gauge, safety goggles, gloves.
• Connect the fuel pressure gauge to the fuel rail test port.
• Start the engine and monitor the fuel pressure; compare it against manufacturer specifications (usually around 40-50 psi).
• If the pressure is low, inspect the fuel pump and fuel filter; replace if necessary.

5. Inspect Air Intake and Vacuum Leaks

• Tools Required: Visual inspection tools, MAF cleaner.
• Inspect the intake manifold and hoses for cracks or loose connections.
• Clean the MAF sensor with MAF cleaner (do not touch the sensor elements).
• If issues are found, replace damaged hoses or gaskets.