PURPOSE: To uniform the outputs of cylinders so as to improve the drivability by sampling the detected values of combustion pressure sensors each of which is provided for each cylinder, on the basis of a signal which is issued every time when the capacity of each of the cylinders is varied by a certain amount synchronously with the revolution of a crankshaft.

CONSTITUTION: A combustion pressure sensor 7 is provided for each cylinder of an engine 1 and the detected values thereof are sent to an operator 14. Faced to a slit plate 3 which is fixed to a crankshaft 2, are arranged a rotary angle sensor 4A which is constituted by a photo sensor and transmits a rotary angle signal at a constant angular interval, a TDC sensor 4B which transmits a TDC signal indicating the top dead center of a certain cylinder, and constant capacity sensors 4C and 4D which transmit signals every time when the capacity of each of the cylinders is varied by a certain amount. The signals detected by those sensors are sent to an amplifier 13. Based on the constant capacity signal from the amplifier 13, operator 14 samples the combustion pressures of the respective cylinders and computes the illustrated mean effective pressure in each cycle of those cylinders and then controls the quantity of injected fuel so that the computed value may come close to the average value of the sum of the illustrated mean effective pressures of the entire cylinders.