System for controlling idling speed in internal combustion engine for vehicle with automatic transmission

Claim 1

In a system for controlling engine idling speed for an internal combustion engine of a vehicle provided with an automatic transmission, the engine being provided with an intake line and a throttle valve arranged therein, said system comprising: a by-pass passageway connected to the intake line so as to by-pass the throttle valve; valve means arranged in the by-pass passageway for controlling the amount of air passing therethrough; means for calculating the degree of opening of the valve means corresponding to a preset parameter corresponding to an intake air amount during a substantially fully closed condition of the throttle valve; and means for producing a signal directed to the valve means for operating the same so that the actual opening of the valve means corresponds to the opening calculated by the calculating means, the improvement wherein the system further comprises apparatus for decreasing shock when the automatic transmission is downshifted, the apparatus comprising means for detecting a shift down operation of the automatic transmission while the vehicle is in an engine braking condition wherein the net torque output of the engine is negative; and means for modifying the calculated degree of opening of the throttle bypass valve means so that the amount of air is increased during the shift down operation, thereby reducing the engine pumping inertia.