how to troubleshoot a misfire on my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Replace Spark Plugs

• Remove the ignition coil cover if applicable.
• Disconnect the ignition coil electrical connectors.
• Remove the bolts securing the ignition coils and pull them out carefully.
• Remove the old spark plugs using a spark plug socket and ratchet.
• Install new spark plugs, ensuring they are gapped correctly to manufacturer specifications (typically around 0.043 inches).
• Reinstall the ignition coils and reconnect the electrical connectors.

3. Inspect and Replace Ignition Coils

• If misfire codes indicate specific cylinders, replace the corresponding ignition coils.
• Remove the faulty ignition coil, using a socket wrench.
• Install the new ignition coil and secure it with the bolts.
• Reconnect the electrical connector.

4. Clean or Replace Fuel Injectors

• If injectors are clogged, use a fuel injector cleaner or replace them.
• Remove the intake manifold if necessary to access the injectors.
• Disconnect fuel lines and electrical connectors from the injectors.
• Remove the old injectors and install the new or cleaned ones.
• Reinstall the intake manifold and reconnect all components.

5. Check and Repair Vacuum Leaks

• Inspect all vacuum lines for cracks or disconnections.
• Replace any damaged vacuum hoses.
• Use a smoke test if necessary to identify hard-to-find leaks.

Tools Required:

• OBD-II scanner
• Socket set (including spark plug socket)
• Ratchet and extensions
• Torque wrench
• Fuel pressure gauge
• Compression tester
• Screwdrivers

Parts Required:

• Spark plugs (new)
• Ignition coils (if defective)
• Fuel injectors (if clogged or damaged)
• Vacuum hoses (if damaged)

Estimated Repair Time: 2-4 hours

Safety Warnings:

• Disconnect the battery before working on electrical components.
• Allow the engine to cool before starting repairs to avoid burns.