my Toyota Corolla E170 (2013-2019) has a rough idle when cold, what's wrong

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is on a level surface and parked in a safe location.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coil or spark plug wires as needed.
  2. Use a spark plug socket to unscrew and remove the old spark plugs.
  3. Inspect the condition of the spark plugs; replace if they are worn or fouled.
  4. Install new spark plugs, ensuring they are gapped correctly (0.043 inches) and torqued to 13 lb-ft.
  5. Reinstall the ignition coil or spark plug wires.

3. Clean or Replace Idle Air Control Valve

• Sub-steps:
  1. Locate the idle air control valve (IAC) on the throttle body.
  2. Disconnect the electrical connector and remove any mounting screws.
  3. Carefully remove the IAC valve and inspect it for carbon buildup.
  4. Clean the valve using carburetor cleaner and a soft brush, or replace it if necessary.
  5. Reinstall the IAC valve and reconnect the electrical connector.

4. Check and Replace Engine Coolant Temperature Sensor (if needed)

• Sub-steps:
  1. Locate the coolant temperature sensor in the engine block.
  2. Disconnect the electrical connector and remove the sensor using a socket.
  3. Install a new coolant temperature sensor, ensuring a proper seal with thread sealant.
  4. Reconnect the electrical connector and verify the connection is secure.