how to diagnose a misfire in my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to avoid electrical shorts.

2. Replace Spark Plugs

• Remove the ignition coils by unscrewing the retaining bolts and gently lifting them off the spark plugs.
• Use a spark plug socket to remove the old spark plugs.
• Inspect the threads and clean them if necessary.
• Install new spark plugs, ensuring they are gapped according to manufacturer specifications (typically 0.043 inches for Toyota).
• Torque the spark plugs to the specified value (usually around 13 lb-ft).

3. Test and Replace Ignition Coils (if necessary)

• If misfire codes indicate a specific cylinder, test the respective ignition coil.
• Replace any faulty ignition coils with new ones, ensuring to apply dielectric grease on the terminals to prevent moisture ingress.

4. Clean or Replace Fuel Injectors

• If fuel injectors are found to be clogged, use a fuel injector cleaner or replace them with new units.
• Reconnect fuel lines and ensure there are no leaks.

5. Inspect and Repair Vacuum Leaks

• Use a smoke tester or spray soapy water around the intake manifold and vacuum hoses to check for leaks.
• Replace any damaged hoses or gasket that may be causing a leak.