1. Idle Air Control (IAC) Valve: The IAC valve regulates the amount of air that bypasses the throttle body, helping to control the engine idle speed. If the IAC valve is faulty or has carbon buildup, it can cause the idle speed to remain high.
2. Throttle Position Sensor (TPS): The TPS provides information about the throttle valve position to the engine control unit (ECU). If the TPS is defective or misadjusted, it can send incorrect signals to the ECU, resulting in a high idle.
3. Vacuum Leaks: Vacuum leaks can cause the engine to run lean, which can lead to a high idle. Check for any loose or cracked vacuum hoses, especially around the intake manifold and throttle body area.
4. Dirty Throttle Body: A dirty throttle body can cause airflow restrictions, resulting in a high idle. Clean the throttle body with a suitable throttle body cleaner and a soft cloth.
5. Faulty Engine Temperature Sensor: The engine temperature sensor provides information about the engine's temperature to the ECU. If the sensor is faulty or provides incorrect readings, it can affect the fuel injection and idle speed control.
6. Faulty Electronic Control Unit (ECU): In some cases, a faulty ECU can cause various engine issues, including a high idle. However, this is generally less common compared to the other causes mentioned above.
If you are not comfortable troubleshooting and resolving these issues yourself, it's recommended to take your Mercury Cougar to a qualified mechanic for proper diagnosis and repair.
