Abstract: A fuel injection controlling device for a two-cycle engine includes an electronic fuel injection system having a fuel injection quantity determining device for determining a fuel injection amount in response to a rotational speed of said engine and a throttle opening. A misfire detecting device is provided for detecting a misfire condition of said engine. Further, a device is provided for decreasing the amount of fuel injection upon transition from a misfire condition to a fired condition. The misfire detecting device includes a sensor for detecting an internal pressure of an intake air path, a storage device for storing therein an output value of the sensor and data of an intake air path internal pressure in a predetermined operating condition of the engine upon normal combustion, and a comparison device for comparing the output value with data read out from the storage means to detect a difference in pressure.