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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to avoid electrical shorts during repairs.

2. Inspect and Replace Spark Plugs

• Remove the ignition coil cover if applicable.
• Use a socket wrench to remove the spark plugs.
• Inspect the spark plugs for signs of wear or carbon buildup.
• Replace spark plugs with OEM or equivalent parts, ensuring the correct gap is set (typically 0.043 inches for most Toyota engines).
• Reinstall the ignition coil and cover.

3. Test and Replace Ignition Coils

• Disconnect the wiring harness from each ignition coil.
• Use a multimeter to check the primary and secondary resistance of each coil (consult the service manual for specific values).
• Replace any faulty ignition coils with new OEM parts.
• Reconnect the wiring harness and ensure all connections are secure.

4. Clean or Replace Fuel Injectors

• Remove the fuel rail assembly if necessary to access the injectors.
• Inspect fuel injectors for cleanliness; use a fuel injector cleaner if needed.
• If injectors are clogged, replace them with new OEM injectors.
• Reinstall the fuel rail assembly ensuring all connections are sealed and secure.

5. Perform Compression Test

• Remove spark plugs to allow for easier access to cylinder compression.
• Insert a compression gauge into each cylinder and crank the engine to measure compression.
• Compare readings to manufacturer specifications (typically 150-200 psi).
• If any cylinder is significantly lower, further investigation may be required to check for valve or piston ring issues.