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 ensure safety while working on electrical components.

2. Inspect and Replace Spark Plugs

• Remove the engine cover (if applicable) using a socket set.
• Carefully disconnect the ignition coil connectors from the spark plugs.
• Remove the ignition coils using a socket or ratchet.
• Extract the spark plugs using a spark plug socket; inspect for wear or fouling.
• Replace spark plugs with new, manufacturer-recommended plugs.
  • Torque to specification (generally around 13 lb-ft) during installation.

3. Inspect Ignition Coils

• Check each ignition coil for cracks, corrosion, or other damages.
• Replace any defective ignition coils with new ones.
• Reinstall ignition coils and reconnect the electrical connectors.

4. Check and Replace Fuel Injectors (if necessary)

• Using a noid light, check each fuel injector connector for signal.
• If a fuel injector is faulty, remove it by disconnecting the electrical connector and fuel line.
• Install a new fuel injector, ensuring to lubricate the O-rings with engine oil for proper sealing.
• Reconnect the fuel line and electrical connector.

5. Vacuum Leak Test

• Inspect all vacuum hoses and connections visually for wear or disconnection.
• Use a smoke tester to identify leaks in the intake manifold or vacuum lines.
• Replace any damaged hoses and recheck for leaks.

6. Compression Test (if necessary)

• Remove spark plugs and disable fuel injectors for safety.
• Insert a compression gauge into each cylinder and crank the engine.
• Compare compression readings against manufacturer specifications; replace engine components as needed if readings are low.