A method of and an apparatus for controlling the revolution speed of an engine, suitable for use in an automobile having an automatic transmission. Flow rate of auxiliary intake air by-passing a throttle valve is controlled by an auxiliary air control valve, the opening period of which is incremented in response to a signal which represents the state of the automatic transmission shifted from neutral range to a power range so as to avoid any reduction in the engine speed or the engine stall. The valve open time is controlled as a function of the engine cooling water temperature.