| 摘要 |
A bypass passage bypassing a throttle valve and communicating a portion upstream of the throttle valve with a portion downstream of the throttle valve is blocked when an engine speed is increased to the upper limit value or more of a predetermined range or the bypass passage is opened when the engine speed is decreased to the lower limit value or less of the predetermined range, whereby the engine speed during idling is controlled to a value within the predetermined range. An idle speed is stabilized by opening the bypass passage immediately after the start and during warm-up process, where the engine speed is particularly instable during idling. Furthermore, the period of time of opening or blocking the bypass passage is shortened in accordance with the increase in a difference between the upper or lower limit of the predetermined range and the engine speed, whereby the engine speed is controlled so as to be quickly to a value within the predetermined range.
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