Does a sensor control the idle speed on V6 3100 engine?

Yes, a sensor plays a crucial role in controlling the idle speed on a V6 3100 engine (and most modern engines). It's not just one sensor, but a combination working together, primarily the Idle Air Control (IAC) valve, which is controlled by the Engine Control Module (ECM). The ECM receives input from various sensors, including the:

* Throttle Position Sensor (TPS): Tells the ECM how much the throttle is open.

* Manifold Absolute Pressure (MAP) sensor: Measures the pressure in the intake manifold.

* Coolant Temperature Sensor (CTS): Indicates the engine coolant temperature.

* Mass Air Flow (MAF) sensor (if equipped): Measures the amount of air entering the engine.

The ECM uses the information from these sensors to adjust the amount of air bypassing the throttle plate via the IAC valve, thus controlling the idle speed. The IAC valve's position directly impacts the idle speed. If any of these sensors fail, it can lead to erratic idle or an inability to maintain a stable idle.