how to fix P0301 misfire code in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

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

2. Inspect and Replace Ignition Components

• Tools Required: Socket set, torque wrench, spark plug socket.
• Sub-steps:
  1. Remove the engine cover if applicable (typically held by bolts or clips).
  2. Disconnect the ignition coil connector for cylinder 1.
  3. Remove the ignition coil using a socket set.
  4. Inspect the spark plug for wear and carbon buildup; replace if necessary.
  5. Install a new spark plug with a torque value of 13 lb-ft (17.6 Nm).
  6. Reinstall the ignition coil and reconnect the connector.

3. Check and Replace Fuel Injector

• Tools Required: Fuel injector puller (if needed), socket set.
• Sub-steps:
  1. If the fuel injector is suspected to be faulty, disconnect the fuel injector connector.
  2. Remove the fuel rail (if necessary) to access the injector.
  3. Replace the injector with a new one, ensuring proper orientation.
  4. Reinstall the fuel rail and reconnect all connectors.

4. Conduct Compression Test

• Tools Required: Compression tester.
• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine and record the compression reading.
  4. Compare the reading to manufacturer specifications (usually around 180-200 psi).
  5. If the reading is low, further investigation into piston rings or valves may be necessary.

5. Inspect for Vacuum Leaks

• Tools Required: Smoke machine or carburetor cleaner.
• Sub-steps:
  1. Visually inspect hoses and gaskets around the intake manifold.
  2. Use a smoke machine to detect leaks; alternatively, spray carburetor cleaner around suspected areas and listen for changes in engine RPM.
  3. Repair or replace any faulty hoses or gaskets.