Abstract: A fuel-air vaporizing apparatus including fuel metering means discharging a regulated fuel flow into a heated airflow within a conduit for subsequent and remote discharge into the air induction system of an engine. A nozzle structure, subjected to vacuum pressure, discharges fuel below an induction regulating valve. Fuel and air linkage, jointly operated by the driver's throttle, actuate said fuel metering means and the air induction regulating valve in a synchronized manner to provide an optimum, completely vaporized fuel-air mixture to the engine. An idle assembly controls engine operation during both idling and other closed throttle conditions. Said idle assembly functions to cut off fuel flow during vehicle deceleration with fuel flow resuming upon certain engine conditions being reached. Temperature responsive means are associated with both the idle assembly and the fuel-air linkage to assure optimum fuel-air ratios throughout a range of engine temperatures.