Abstract: A vehicle engine has a throttle stop positionable in response to an actuator command signal to determine engine idle speed. Apparatus is provided to generate a speed error signal having both an absolute value and a further characteristic indicative of high or low speed; and further apparatus is provided including a memory effective to store actuator command signals corresponding to specific speed error signals and speed correction apparatus effective to obtain an actuator command signal from the memory corresponding to each speed error signal and supply the actuator command signal to the throttle stop positioning apparatus to correct engine idle speed in the direction of a predetermined desired engine idle speed.

Abstract: A vehicle engine includes throttle stop control apparatus including means effective to store a plurality of induction passage pressure numbers corresponding to specified values of engine speed. Further apparatus measures engine speed and induction passage pressure and compares the induction passage pressure with a control reference number derived from the induction passage pressure reference number corresponding to the measured engine speed. When the throttle is in the idle position and the induction passage pressure signal exceeds the reference, a throttle stop control loop is closed on engine speed to maintain a predetermined engine idle speed. However, when the throttle is in the idle position and the induction passage pressure signal does not exceed the reference, the throttle stop control loop is closed on induction passage pressure to maintain substantially the reference pressure, whereby throttle position during vehicle coastdown is controlled according to a predetermined stored schedule.