A single point fuel injection throttle body assembly including an idle air control circuit having an port opening into main intake bores downstream of the point of fuel distribution into the air stream. When the idle air control circuit is open, an air/fuel mixture, rather than simply air, is drawn into the into the intake manifold, thereby reducing the tendency for a lean fuel mixture at idle. A unique engine control unit “feed forward” algorithm controls the fuel injection as a function of the position of the idle air control motor so that as the idle air control circuit is opened, the pulse widths of the fuel injector signals are increased. This feature allows the initial open-loop-based fuel mixture supplied by system to be more accurate and eliminates rough unstable idle associated with closed-loop control lag times.