What is the IAC valve in a fuel injection system?

The IAC (Idle Air Control) valve in a fuel injection system regulates the amount of air entering the engine during idle conditions. It allows for precise control of engine idle speed by adjusting airflow based on signals from the engine control unit (ECU), which takes into account factors like engine temperature and load. A properly functioning IAC valve helps maintain a stable idle, improves fuel efficiency, and reduces emissions. If it malfunctions, it can lead to issues such as rough idling or stalling.