how to diagnose a misfire in my Toyota Highlander XU70 (2020-Present)?

Solution

1. Preparation

• Gather tools and parts (OBD-II scanner, spark plug socket, multimeter, fuel pressure gauge, replacement spark plugs, ignition coils, or fuel injectors as needed).
• Disconnect the negative battery terminal to prevent electrical shock.

2. Replace Spark Plugs

• Remove the engine cover (if applicable) to access the spark plugs.
• Using a spark plug socket, carefully unscrew and remove the old spark plugs.
• Inspect the thread and seat for any debris; clean if necessary.
• Install new spark plugs by hand to avoid cross-threading, then torque to manufacturer's specification (typically around 13-16 lb-ft).

3. Test and Replace Ignition Coils

• Disconnect the wiring harness from the ignition coil.
• Using a multimeter, measure the resistance of the coil; refer to the service manual for specific resistance values.
• If the coil is out of specification, replace it with a new one, ensuring a secure connection.

4. Inspect and Clean Fuel Injectors

• Connect a fuel pressure gauge to the fuel rail and turn the ignition on (do not start) to check for proper pressure.
• If pressure is low, consider replacing the fuel filter or fuel pump.
• For cleaning, use an injector cleaning kit or replace the injectors as necessary.

5. Check for Vacuum Leaks

• With the engine running, use a smoke machine or carburetor cleaner around vacuum lines and intake manifold to detect leaks.
• Repair or replace any damaged vacuum lines found during the inspection.

6. Verify Engine Timing

• Remove the timing cover and inspect the alignment of the timing marks.
• If the timing is off, adjust or replace the timing belt or chain as necessary, following the manufacturer's specifications.