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

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shocks.

2. Replace Spark Plugs

• Tools Required: Socket set, spark plug socket, torque wrench
• Remove the engine cover if necessary.
• Disconnect the ignition coil connectors.
• Remove the ignition coils by unscrewing them and gently pulling them out.
• Use a spark plug socket to remove the old spark plugs. Inspect and replace with new plugs, ensuring they are gapped correctly (refer to manufacturer specifications).
• Torque the spark plugs to the specified value (usually around 13-15 ft-lbs).
• Reinstall the ignition coils and reconnect the connectors.

3. Check and Replace Ignition Coils

• If misfire codes indicate specific cylinders, replace the associated ignition coils.
• Tools Required: Socket set, torque wrench
• Remove the ignition coils as described in the previous step.
• Install new ignition coils, ensuring they are seated properly.
• Torque the bolts to the specified value (typically around 8-10 ft-lbs).

4. Inspect and Clean Fuel Injectors

• If fuel injectors are suspected, remove them for cleaning or replacement.
• Tools Required: Fuel injector puller, cleaning solution, O-rings
• Relieve fuel pressure by removing the fuel pump fuse and starting the engine until it stalls.
• Disconnect the fuel lines and electrical connectors from the injectors.
• Remove the fuel rail with the injectors attached.
• Clean the injectors using a specialized cleaning kit or replace them with new ones.
• Reinstall the fuel rail with new O-rings and ensure all connections are secure.

5. Perform a Compression Test

• If misfires persist, check cylinder compression.
• Tools Required: Compression gauge
• Remove spark plugs and install the compression gauge in the cylinder.
• Crank the engine and record the compression reading.
• Repeat for all cylinders and compare values to manufacturer specifications.