| 摘要 |
PROBLEM TO BE SOLVED: To prevent backward flow of exhaust gas to an intake side during valve overlap period until engine stop and generation of airflow noise in closing an idle control valve caused by negative pressure in an intake pipe by avoiding large negative pressure's remaining in the intake pipe in downstream of a throttle valve when a standard position of the stepping motor type idle control valve is calibrated by ignition switch off. SOLUTION: Air is introduced to downstream of the throttle valve with keeping opening of the ISC valve equal to or greater than an established opening at ignition switch off to make pressure in the intake pipe in downstream of the throttle valve close to atmospheric pressure. Consequently, backward flow of exhaust gas to an intake system caused by valve overlap is avoided to prevent deterioration of re-startability of the engine, and generation of unpleasant airglow noise in opening ISC valve to prepare for next engine start after calibration at the full close position is prevented.
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