PURPOSE: To minimize electric power loss, and eliminate disturbance to operating conditions by setting the position of an idle air adjuster to a non-driving position at any load area other than idling or engine braking, and other than idling or engine braking, monitoring driving parameter variation so as to drive at a proper position.

CONSTITUTION: Idle control for an internal combustion engine 10 involving an idle air adjuster 11 is controlled by output from a prior controller 15 based on the temperature of the engine or the like. In the case of engine braking, an operating signal is inputted into the air adjuster 11 from a memory 16 through a selector 18. The air adjuster is kept under a non-driving condition at any load area other than idling or engine braking. In any case of other than idling or engine braking, it is driven at a proper position in response to a parameter variation, thus it is possible to eliminate electric power loss and disturbance to driving conditions.