* Idle air control (IAC) valve: The IAC valve is responsible for controlling the amount of air that bypasses the throttle body at idle. A faulty IAC valve can cause the engine to idle too high or too low.
* Vacuum leaks: A vacuum leak can cause the engine to run lean, which can lead to a high idle.
* Throttle position sensor (TPS): The TPS is responsible for sensing the position of the throttle blade. A faulty TPS can cause the engine to idle too high or too low.
* Idle mixture: The idle mixture is the amount of fuel that is mixed with air at idle. Too much fuel can cause the engine to idle high, while too little fuel can cause it to idle low.
* Oxygen sensor: The oxygen sensor measures the amount of oxygen in the exhaust. A faulty oxygen sensor can cause the engine to run rich or lean, which can lead to a high idle.
If your 1978 Corvette is idling too high or too low, it's important to have it diagnosed by a qualified mechanic.
