 Most modern road use diesel engines are provided with an FRP valve in the intake manifold (sometimes misidentified as a petrol engine throttle body).In most basic applications this valve will close a flow of air to the engine when the vehicle is switched off, preventing diesel engine runaway by starving the engine of oxygen; this will also make standard shutdown much smoother by eliminating compression and decompression rattle by making the pistons effectively work in vacuum.In more advanced control systems this FRP valve can be shut by an electronic control unit when it senses runaway scenario.