executing various control programs a read only memory 12 storing therein the control programs and a random access memory 13 primarily for temporarily storing data the processor 11 is connected via an input circuit 14 to various sensors and switches some of them are not shown such as the crank angle sensor 20 the cylinder discrimination sensor 30 an ignition switch 40 an intake air amount sensor an intake air temperature sensor and a water temperature sensor and is also connected via an output circuit 15 to various driving circuits only those corresponding to elements 50 and 60 are indicated by reference characters 51 and 61 for driving various actuators including a fuel injection valve 50 and for driving a warning lamp 60 the apparatus of the present embodiment which is mounted on the 6 cylinder engine wherein ignition is performed in the order of the cylinder number is designed so that when for example an end a leading end 21c 39 or a trailing end of the third vane 21c passes through the detector 22 the crankshaft enters into a first crankshaft rotational angle area corresponding to either one of the first cylinder and the fourth cylinder preferably corresponding primarily to an expanding stroke of the cylinder concerned which cylinders constitute a first cylinder group and when an end of the first vane 21a passes through the detector 22 the crankshaft leaves the first rotational angle area likewise when an end of the first vane 21a passes through the detector the crankshaft enters into a second crankshaft rotational angle area corresponding to either one of the second and fifth cylinders which constitute a second cylinder group and.