Abstract: A diagnosis of deterioration and/or normality of an exhaust gas purifying catalyst is made by comparing a ratio of reversal frequencies of outputs from oxygen sensors disposed on opposite sides of the exhaust gas purifying catalyst with a threshold ratio. Discrimination is performed on both normality and deterioration in a standard gas quantity zone, on only normality in a large gas quantity zone, and on only deterioration in a small gas quantity zone, and nothing is made in an extra large gas quantity zone.

Abstract: A catalyst degradation determination apparatus having O.sub.2 sensors provided at the upstream and downstream of a catalyst, detects degradation of the catalyst by, during A/F ratio feed-back control since an engine has been started, comparing an integrated value of output values from the upstream O.sub.2 sensor with that of output values from the downstream O.sub.2 sensor. Upon starting integration of the output values from the respective O.sub.2 sensors, change of activated status of the catalyst is judged. If the status of the catalyst is approximately the same as a previous status, the integration is started with previous integrated values. On the other hand, if the status of the catalyst is different from the previous status, the previous integrated values are reset, and the integration of the output values from the respective O.sub.2 sensors is started from the beginning. This prevents erroneous catalyst degradation determination.

Abstract: An engine speed control system causes an engine, equipped with an automatic transmission which shifts up according to predetermined shift schedules, to reduce its output at a predetermined engine speed so as to protect the engine by preventing the engine from being subjected to "over-revolution." The predetermined engine speed is changed according to engine operating conditions such as a decrease in engine temperature. Simultaneously, a shift-up vehicle speed, at which the automatic transmission shifts itself up, is decreased according to engine operating conditions and, more particularly, engine temperatures and throttle openings. As a result, an up-shift of the automatic transmission properly takes place, even when the vehicle travels at lower speeds.

Abstract: An intake system for an automobile engine with a manual transmission or an automatic transmission has a throttle valve disposed in an intake passage for distributing air into cylinders of the engine. A supplementary air distributor provided in association with the intake passage supplementarily distributes air into the intake passage between the throttle valve and engine. The supplementary air distributor is controlled by a controller to distribute different amount of supplementary air according to engine operating conditions. The controller is correctively controlled to vary the amount of supplementary air, by the supplementary air distributor according to atmospheric pressure for every distribution, so as to distribute a larger amount of supplementary air do an automobile engine with an automatic transmission than do an automobile engine with a manual transmission at the same atmospheric pressure.

Abstract: A fuel injection control system is designed to be commonly available to an engine with a manual transmission and an engine with an automatic transmission. The internal combustion engine has a fuel injection device for delivering different amounts of fuel to the engine according to engine operating conditions. The fuel injection control system causes the fuel injection device to make an increase in fuel amount when the engine operates in a specific zone of engine operating conditions defined by engine operating speeds and loads. When the engine operating condition remains in the specific zone, the control system makes the increase in fuel amount with a time delay from a time the engine operating condition changes into the specific zone.

Abstract: A fuel control system for an automobile engine includes various sensors for detecting the running conditions of the engine, an injector or injectors for supplying fuel to the engine, and a control unit for reducing or cutting the amount of fuel to be supplied to the engine in response to the sensors at the time of deceleration and for controlling the injectors so that the amount of fuel to be supplied to the engine at the time of removal of deceleration is less than the normal amount corresponding to the running conditions of the engine. The control unit further operates so that the amount of reduction of the fuel supply is less in an engine equipped with an automatic transmission than in an engine equipped with a manual transmission. The control unit also operates so that the initial amount of fuel to be supplied to the engine at the time of removal of deceleration is less in the engine equipped with the manual transmission than in the engine equipped with the automatic transmission.

Abstract: An engine control system of an automotive engine cooperates with an engine driven air conditioning system which is restrictively driven when the engine operates in a predetermined operating condition. The engine control system includes a pressure sensor to detect an atmospheric pressure at which the engine operates. The predetermined condition is changed according to the atmospheric pressure.

Abstract: A system for controlling idling speed of an internal combustion engine in which a speed sensor senses rotational speed of the engine. A determinator is provided for determining whether the engine is in an idling state. An output adjustor adjusts engine output when the engine is determined to be in the idling state by the determinator. A memory stores a control variable of the output adjustor in the form of a characteristic in which engine output rises approximately in proportion to a difference between a predetermined target idling speed and an actual idling speed with engine speed serving as a parameter. A control acts responsive to outputs from the determinator and the speed sensor for obtaining from the memory a control variable corresponding to engine speed at idling, and for controlling the output adjustor on the basis of the control variable.

Abstract: In an automatic transmission control system, completion of gear-shifting is detected on the basis of both the rate of change in rotational speed of the output shaft of the torque converter and the rotational speed at which the output shaft of the torque converter is expected to rotate. That is, a rotational speed range within which the rotational speed of the output shaft of the torque converter is expected to fall upon completion of the gear-shifting is determined taking into account the rotational speed of the output shaft of the torque converter upon initiation of the gear-shifting and the gear ratio, and it is determined that the gear-shifting is completed when the rotational speed of the output shaft of the torque converter falls within the predetermined rotational speed range and the rate of change in rotational speed of the output shaft of the torque converter is reduced below a predetermined value.

Abstract: A lock-up control system for an automatic transmission including a torque converter coupled with an engine, a power transmitting gear arrangement controlled by a gear ratio control device in accordance with a shifting up or down signal, and a lock-up clutch provided for locking up the output shaft of the torque converter to the output shaft of the engine. The lock-up control system comprises lock-up operation control apparatus causing the lock-up clutch to be in its inoperative state when the gear ratio control device performs the control with the shifting up or down signal, and lock-up command device for preventing the lock-up operation control apparatus from causing the lock-up clutch to be in its inoperative state until a predetermined reductive variation in the speed of the output shaft of the torque converter arises after the shifting up signal is supplied to the gear ratio control device under the condition in which the lock-up clutch is in operation.