Abstract: A vehicle is driven by an internal combustion engine having an air induction passage with an idle air control valve positionable by a stepping motor in response to valve opening and valve closing pulses. A counter normally counts the pulses arithmetically to provide an indication of valve position. In order to bring the counter and valve position into accord, counter reset apparatus is effective, when actuated, to generate a predetermined number of valve closing pulses sufficient to stall the stepping motor against the stop, reset the counter to a predetermined reference count and generate a predetermined number of valve opening pulses to return the idle air control valve to a desired operating position with the counter counting such pulses in the normal manner.

Abstract: Idle air control apparatus for a vehicle driving internal combustion engine having an air induction passage includes a control valve in the air induction passage controlled by a stepper motor in response to the arithmetic count of applied electrical pulses, a register effective to store a valve control number representing the currently desired position of the control valve, apparatus effective upon occurrence of a predetermined engine loading event to change the valve control number in response thereto, an up-down counter effective to arithmetically count the pulses applied to the stepper motor and thus indicate actual control valve position, a closed loop control effective to compare the contents of the up-down counter and register and apply pulses to the stepper motor at the first predetermined rate to reduce any difference therebetween and a speed trim loop active only during occurrence of a predetermined steady state idle condition to compare actual engine speed with the desired engine idle speed and arit