why does my Toyota Highlander Third Generation (2014-2019) have rough idle when cold

Solution

1. Preparation

• Gather tools and parts required for the repair.
• 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

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coils from the spark plugs.
  3. Use a socket wrench to remove the old spark plugs.
  4. Inspect the spark plugs for wear; replace with OEM equivalents if necessary.
  5. Reinstall the new spark plugs and reconnect the ignition coils.
• Tools Required: Socket set, torque wrench.
• Safety Warnings: Ensure the engine is cool to prevent burns.

3. Check and Replace Coolant Temperature Sensor

• Sub-steps:
  1. Locate the coolant temperature sensor on the engine.
  2. Disconnect the electrical connector from the sensor.
  3. Remove the sensor using a wrench or socket.
  4. Install the new coolant temperature sensor and reconnect the electrical connector.
• Tools Required: Wrench set, socket set.
• Safety Warnings: Allow the engine to cool before working on the cooling system.

4. Clean Throttle Body

• Sub-steps:
  1. Remove the air intake duct to access the throttle body.
  2. Use throttle body cleaner and a soft cloth to clean the throttle plate and surrounding areas.
  3. Reinstall the air intake duct securely.
• Tools Required: Throttle body cleaner, soft cloth.
• Safety Warnings: Ensure the area is well-ventilated while using chemical cleaners.

5. Check Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail to access the fuel injectors.
  2. Inspect each injector for clogs or leaks.
  3. Clean or replace any faulty injectors as necessary.
  4. Reinstall the fuel rail and ensure all connections are secure.
• Tools Required: Fuel pressure gauge, socket set.
• Safety Warnings: Relieve fuel pressure before disconnecting fuel lines to avoid spills.