Abstract: A cruise control apparatus includes an actuator adapted to cooperate with an accelerator to open and close an intake throttle valve to a specified opening position, and to prevent the throttle valve from returning to a fully closed position to thereby maintain a selected vehicle speed. A control unit is provided to control the actuator so that movement of the throttle valve to a fully closed position is retarded for a predetermined time period after disengaging the cruise control function. The control unit controls the actuator so as to permit free movement of the throttle valve toward the fully closed position after the predetermined time period.

Abstract: An examination device for use with a vehicle constant speed control apparatus which adjusts the speed of a vehicle to a predetermined speed in response to a constant speed control command includes a first switching arrangement for connecting and disconnecting an electric power supply and the apparatus, and a second switching arrangement for delivering the constant speed control command. A control arrangement is provided for inhibiting the constant speed control of the vehicle when the second switching arrangement is on at the time the first switching arrangement is connected.

Abstract: A diagnosis arrangement for a vehicle engine controller includes a control arrangement which examines a signal identifying the activation of an auxiliary control system of the engine and which determines whether the auxiliary engine control system, which includes a device controlled by a particular control program selected from a plurality of programs stored therein, is actuated in a manner corresponding to the selected control program.

Abstract: An apparatus for controlling a carburetor of a combustion engine includes: a throttle-opening detector switch for detecting that a throttle valve of the carburetor is opened within a predetermined degree of throttle opening; an idle-up mechanism for making the throttle valve perform an idling-up operation; a fuel-cut mechanism for cutting a slow speed fuel supply of the carburetor; and a control unit adapted to allow the idle-up mechanism to perform the idling-up operation under a predetermined load applied to the engine and allow the fuel-cut mechanism to cut the slow speed fuel supply at a reduced speed of the engine when the throttle-opening detector switch detects that the throttle valve of the carburetor is within the predetermined degree of throttle opening. The control unit also includes an arrangement responsive to detection that the throttle valve is not within the predetermined range for inhibiting the idle-up mechanism.

Abstract: An air-fuel ratio control apparatus for an internal combustion engine supplies an output signal from an O.sub.2 sensor detecting the concentration of oxygen in the exhaust gas to an electronic control unit having a microcomputer, and a control valve of the carburetor is controlled by a control signal from the microcomputer so as to control the air-fuel ratio in a feedback manner. A desired upper limit value is set for the control signal and, when the control signal exceeds this upper limit value in a transient operating condition of the engine, when its operating state is shifted from an idling state to a partial operating state, the microcomputer promptly changes the rich air-fuel ratio to a proper value.

Abstract: In a method of controlling an air-fuel ratio for an internal combustion engine, a control section feedback-controls an electronically controlled carburetor in response to a signal from an O.sub.2 sensor which detects the concentration of O.sub.2 in the exhaust gas. When the O.sub.2 sensor outputs a rich signal for a predetermined time period after the air-fuel ratio is leaned upon deceleration of the engine, the rich air-fuel ratio is instantaneously and forcibly leaned by the control section in order to rapidly return it to a proper value. Thereafter, ordinary feedback control is resumed. With this method, the quantity of harmful exhaust gas components such as CO or the like can be reduced without making the operational performance of the engine deteriorate.