Abstract: In a closed loop fuel injection system for an internal combustion engine, a control system responding to several engine operating conditions and to rich fuel power demands operates to normalize the air/fuel ratio to a fixed air/fuel ratio. In the preferred embodiment the system responds to the operating temperature of a gas sensor to effectively remove the influence of the sensor control signals at nonoperational temperature upon the air/fuel ratio developed by the electronic control unit. In addition transducers responding to engine speed, wide open throttle, and coolant temperatures generate control signals to the control system indicating a requirement for engine operation of normalized air/fuel ratio.