To provide a control device of idle engine speed of an internal combustion engine capable of accurately positioning a step motor without addition of a battery.
This device comprises a storage means 11 for storing the number of steps P stop in an engine stop, a means 56 for driving the step motor on the basis of the number of target position steps Pt representing a target position of the step motor and the number of present position steps Px representing a present position of the step motor and an idle state determination means 52 for determining whether idling is in a normal state or not. When starting of an engine, the number of the step P stop in the engine stop is registered as the number of the present position steps. When idling is determined to be in the normal state, the number of the present position steps is rewritten by the number of reference steps which is a predetermined constant and the rewritten number of the present position steps is stored as the number of the reference steps in the idling.
URAKI MAMORU
ANDO HIDEAKI
ITO NOBUHIKO
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