how to diagnose a misfire in my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and materials needed for the job, including an OBD-II scanner, spark plug socket, torque wrench, and multimeter.
• Ensure the engine is turned off and cool before starting any work.

2. Replace Spark Plugs

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the battery (negative terminal) to prevent any electrical shorts.
  3. Use a spark plug socket to remove the old spark plugs.
  4. Inspect the old spark plugs for wear, carbon build-up, or damage.
  5. Install new spark plugs, ensuring they are gapped to manufacturer specifications (typically 0.043 inches for the Highlander).
  6. Torque the spark plugs to the manufacturer-recommended value (usually around 13 ft-lbs).

3. Inspect and Replace Ignition Coils

• Sub-steps:
  1. Remove the connector from the ignition coil.
  2. Use a socket to remove the ignition coil from its mounting.
  3. Inspect the ignition coil for cracks or signs of wear.
  4. Replace any faulty ignition coils with new ones, ensuring they are seated properly.
  5. Reconnect the electrical connector.

4. Test Fuel Injectors

• Sub-steps:
  1. Use a fuel pressure gauge to check the fuel pressure against specifications.
  2. If pressure is low, check the fuel pump and filter for proper operation.
  3. Inspect fuel injectors for clogs or electrical issues using a multimeter.
  4. Clean or replace any faulty injectors as necessary.

5. Check for Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks, breaks, or loose connections.
  2. Use a smoke machine or carburetor cleaner to identify leaks around the intake manifold.
  3. Replace any damaged hoses or seals.