High Quality Content by WIKIPEDIA articles! Idling comes from idle which means absence of motion. In the present case IDLING relates to a running engine that is powering a vehicle when it is not moving. An idling engine consumes only enough power to keep itself and its accessories running, therefore, producing no usable power to the drive train. On a school bus, the practice is actually beneficial to the engine during pre-route. It warms the engine and circulates the fluids, preventing the interaction of cold parts, reducing friction and maintaining maximum driving efficiency during route.