Abstract: A fuel injection control system has a detector for detecting acceleration of an engine and for producing an acceleration signal, an air-conditioner switch for producing an air-conditioner signal when the air-conditioner switch is closed. An auxiliary injection signal generator is provided for producing an auxiliary injection pulse width first signal in response to the acceleration signal and air-conditioner signal. The first signal is injected by the auxiliary injection pulse width when the acceleration signal is detected. The auxiliary injection pulse width first signal has a smaller value than a second signal when the air-conditioner switch is opened, thereby reducing auxiliary injection pulse width.