why does my Toyota Highlander XU70 (2020-Present) have a rough idle when cold

Solution

1. Preparation

• Gather all tools and parts before starting the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery negative terminal for safety.

2. Inspect and Replace the Engine Coolant Temperature Sensor

• Locate the engine coolant temperature sensor.
• Disconnect the wiring harness from the sensor.
• Remove the sensor using a socket wrench.
• Install the new sensor by reversing the removal steps and ensuring it is torqued to manufacturer specifications.
• Reconnect the wiring harness.

3. Clean the Throttle Body

• Remove the air intake duct connected to the throttle body.
• Use throttle body cleaner and a soft cloth to carefully clean the throttle plate and surrounding areas.
• Reinstall the air intake duct securely.

4. Inspect and Replace Spark Plugs

• Remove the ignition coil covers if necessary.
• Disconnect the ignition coils from the spark plugs.
• Use a spark plug socket to remove the old spark plugs.
• Install new spark plugs, ensuring they are gapped according to manufacturer specifications.
• Reconnect the ignition coils and covers.

5. Check and Replace Fuel Filter (if applicable)

• Locate the fuel filter as per the vehicle’s service manual.
• Relieve the fuel pressure by removing the fuel pump fuse and running the engine until it stalls.
• Disconnect the fuel lines from the filter carefully.
• Remove and replace the filter, ensuring proper orientation.
• Reconnect the fuel lines and replace the fuel pump fuse.