how to resolve P0300 random misfire detected in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Ignition Components

1. Remove Engine Cover (if applicable)
   • Use a socket set to remove bolts securing the engine cover.
2. Access Spark Plugs
   • Remove the ignition coils by unplugging the electrical connectors and unscrewing them.
   • Use a spark plug socket to remove the spark plugs.
3. Inspect Spark Plugs
   • Check for signs of wear, carbon buildup, or damage; replace if necessary.
   • Torque specifications for spark plugs: 13 lb-ft (18 Nm).
4. Replace Ignition Coils (if defective)
   • If any coils are found to be faulty, replace them with new ones.
   • Ensure proper seating and torque them to manufacturer specifications (usually around 8 lb-ft or 11 Nm).

3. Inspect Fuel System

1. Check Fuel Pressure
   • Attach a fuel pressure gauge to the fuel rail and compare the reading to manufacturer specifications (typically 50-60 psi).
2. Clean or Replace Fuel Injectors
   • If pressure is low or injectors are clogged, use a fuel injector cleaner or replace them.

4. Inspect for Vacuum Leaks

1. Visual Inspection
   • Inspect all vacuum hoses and intake manifold for cracks or disconnections.
2. Use Smoke Test
   • If necessary, perform a smoke test to identify hard-to-find leaks.

5. Verify Exhaust System

1. Inspect for Blockages
   • Check for any restrictions in the exhaust system (e.g., clogged catalytic converter).
2. Check O2 Sensors
   • Ensure that oxygen sensors are functioning properly, as they can affect air-fuel mixture.