* Throttle Position Sensor (TPS): This sensor tells the computer the throttle's position. At idle, the TPS indicates a very low or closed throttle position.
* Idle Air Control (IAC) Valve: This is the most direct component affecting idle speed. It's a small valve that controls the amount of air bypassing the throttle plate. The engine computer adjusts the IAC valve opening to maintain the desired idle speed. It's usually located on the throttle body.
* Throttle Body: This houses the throttle plate and the IAC valve.
* Engine Control Module (ECM) / Computer: This is the "brain" that monitors various sensors (like the TPS, coolant temperature sensor, etc.) and adjusts the IAC valve to keep the idle speed within a pre-programmed range.
* Fast Idle Cam: Some older, carbureted 350s might have a fast idle cam on the carburetor that increases idle speed when the engine is cold.
So, while the IAC valve on the throttle body is the closest thing to a single "idle" component, the idle speed is a result of the entire system working in concert.
