PURPOSE: To improve the convergent capability of an engine speed to a target idle speed.

CONSTITUTION: In a vehicle with manual transmission, during deceleration of the vehicle, an undershoot occurs in which an engine speed is lowered rapidly to below the idle speed after a clutch is disengaged. After that, the speed is converged and stabilized to near the idle speed. Also the engine operating conditions such as undershoot areas, engine speed in the stabilized rotating areas after these areas, and air intake pipe pressure vary according to the loads of engine auxiliary equipment such as air conditioning device. Then either of an undershoot area or stabilized rotating area is selected according to a clutch disengaging timing during the deceleration of a vehicle, and operating parameters which increase or decrease according to the loads of the engine accessory in these areas are obtained from the engine speed. Based on these operating parameters, the controlled variable of an ISC valve is calculated and the ISC valve is controlled so as to convert the engine speed immediately to a target idle speed immediately after stopping of the vehicle.