* Idle Air Control (IAC) valve is dirty or faulty: The IAC valve controls the amount of air that bypasses the throttle body, and it can get dirty or faulty over time. This can cause the engine to idle rough or surge.
* Vacuum leak: If there is a vacuum leak, it can cause the engine to run lean, which can lead to a high idle.
* Throttle position sensor (TPS) is faulty: The TPS tells the engine computer how far the throttle is open, and it can get faulty over time. This can cause the engine to idle high.
* Fuel injector is dirty or faulty: If a fuel injector is dirty or faulty, it can spray too much or too little fuel, which can cause the engine to idle rough or surge.
* Fuel pressure is too low: If the fuel pressure is too low, it can cause the engine to run lean, which can lead to a high idle.
To troubleshoot the problem, you should first check the IAC valve, vacuum hoses, TPS, and fuel injectors. If any of these components are dirty or faulty, you will need to replace them.
