why does my Toyota Corolla E140 (2006-2013) have a rough idle when cold

Solution

1. Preparation

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

2. Inspect and Replace Spark Plugs

• Sub-steps:
  • Remove the ignition coil cover if applicable.
  • Disconnect the ignition coils from the spark plugs.
  • Remove the spark plugs using a socket wrench.
  • Inspect the spark plugs for wear or deposits; replace if necessary.
  • Install new spark plugs, tightening to the manufacturer’s specified torque (usually around 13-16 lb-ft).

3. Check and Clean the MAF Sensor

• Sub-steps:
  • Locate the MAF sensor in the air intake duct.
  • Disconnect the electrical connector and remove the sensor from the duct.
  • Use MAF sensor cleaner to gently clean the sensor element.
  • Reinstall the MAF sensor and reconnect the electrical connector.

4. Inspect and Replace the Engine Coolant Temperature Sensor

• Sub-steps:
  • Locate the ECT sensor, typically found near the thermostat housing.
  • Disconnect the electrical connector and remove the sensor using a wrench.
  • Install a new ECT sensor and reconnect the electrical connector.

5. Check for Air Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses connected to the intake manifold for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to find leaks around the intake manifold seals.
  • Replace any damaged hoses or seals as necessary.