Question on speed sensor & standard transmission

In general, a speed sensor is part of the idle speed control. If the throttle is closed and speed is zero, the PCM regulates idle speed. Idle speed, is not adjusted when coasting, where speed is not zero. If the PCM thinks the speed is zero at coast, idle control cuts back on by pass air attempting to bring engine speed down, but results in stall when coming to stop, due to delay in control to raise speed again, from over speed cut.

If there is a TB bypass air adjustment, it can be set where the minimum idle speed is maintaned, when idle control is at minimum. That will avoid stalling, yet control idle speed for other loading conditions.