Abstract: A throttle position sensor is provided for detecting opening degree of the throttle valve at regular intervals to produce an opening degree signal dependent on the detected opening degree. A memory has a stored opening degree signal. A detected opening degree signal detected by the sensor is compared with an opening degree signal stored in the memory. The stored opening degree signal is rewritten with the detected opening degree signal when the latter is larger than the former. Thus, a signal representing a maximum opening degree is stored in the memory.

Abstract: A system for controlling speed of an engine for a motor vehicle having an air-conditioner at idling of an automotive engine. The engine has a fuel injection system, a bypass provided around a throttle valve, an auxiliary air valve, and a control unit responsive to the closing of an air-conditioner switch for the air-conditioner for opening the auxiliary air valve, thereby increasing intake air. In response to the closing of the air-conditioner switch the quantity of fuel injected in the engine is temporarily increased, thereby increasing engine speed in accordance with the increase of the intake air.

Abstract: An engine has a bypass around a throttle valve and a solenoid operated idle speed control valve provided in the bypass. The control valve is driven by driving pulses duty ratio of which is dependent on a coolant temperature and an old learning correction value. Temperature of a solenoid of the control valve is converted to voltage. A map is provided for storing normal temperature duty ratios, one of which is derived from the map in dependence on duty ratio of the driving pulses and the voltage. Difference between the duty ratio of the driving pulses and the derived normal temperature duty ratio is stored in a memory. When an ignition switch is turned off, the difference is added to the old learning correction value to produce a new learning correction value. The new learning correction value is used for a subsequent engine operation instead of the old learning correction value.

Abstract: An air-fuel ratio control system for an engine has integrating means for integrating an error signal which is the difference between a reference voltage and an output voltage of an O.sub.2 -sensor and for producing an integration signal. In response to the integration signal, the air-fuel ratio is controlled to a desired value. When fuel vapor in a canister of the engine is purged, an integration constant of the integrating means is increased for a predetermined time in order to allow a deviation of the air-fuel ratio to quickly converge.

Abstract: An air-fuel ratio control system for an engine has a feedback control system operated in accordance with an output voltage of an O.sub.2 -sensor. When the output voltage becomes higher than a reference voltage, the operation of the feedback control system starts. The reference voltage is set to a high level when the engine is started, and set to a low level when a set time elapses after the starting of the engine.

Abstract: A system has an oxygen sensor, a proportion and integration circuit responsive to the output of the oxygen sensor for producing a PI signal at a constant of proportionality and a constant of integration and for controlling the air-fuel ratio of mixture to stoichiometry. The period of the output of the oxygen sensor is compared with a reference value by a comparator. When the period is longer than the reference value, the constants of proportionality and integration are changed so as to correct the deviation of the air-fuel ratio from stoichiometry.

Abstract: An air-fuel ratio control system for an internal combustion engine comprises an induction passage, a carburetor, an on-off type electromagnetic valve for correcting the air-fuel ratio of the air-fuel mixture supplied to the carburetor, an O.sub.2 -sensor for detecting oxygen concentration of exhaust gases, and a feedback control circuit responsive to the output of the O.sub.2 -sensor for producing pulses for driving said electromagnetic valve for correcting the air-fuel ratio.An engine speed detecting circuit is provided for producing an output signal which varies with the engine speed; and a frequency changing circuit is provided to be responsive to the output signal of the engine speed detecting for changing the frequency of the pulses whereby the electromagnetic valve may be prevented from resonating with the vibration of the engine and with the pulsations of induced air.

Abstract: An air-fuel ratio control system for an internal combustion engine having a two-barrel carburetor comprising a primary side having a main metering system and a slow speed system and a secondary side having a main metering system. Two on-off electro-magnetic valves are provided for correcting the air to be supplied to air bleeds of both the primary and secondary sides for correcting air-fuel ratio of the air-fuel mixture supplied by the carburetor.A first passage is provided for connecting the slow speed system of the primary side to one of the electromagnetic valves, a second passage is adapted to connect the main metering system of the secondary side to the one of the electromagnetic valves; and a third passage is provided connecting the main metering system of the primary side to the other electromagnetic valve.A change-over valve is provided for changing the connection between the electromagnetic valve and first and second passages.

Abstract: A system for controlling air-fuel ratio for a carburetor for an internal combustion engine having an intake passage, on air-fuel mixture supply device, a throttle valve, an exhaust passage, a detector such as an oxygen sensor for detecting the concentration of oxygen in the exhaust gases, an on-off type electromagnetic valve for correcting the air-fuel mixture and an electronic controller.The electronic controller comprises a comparing circuit for comparing the output signal of the detector with a reference, a proportional and integration circuit for producing a control signal connected to the comparing circuit, a triangular wave pulse generator, and a driving circuit for producing square wave pulses for driving the on-off type electromagnetic valve from the control signals of the proportional and integration circuit and of the triangular wave pulse, generator for controlling the air-fuel ratio to a valve approximately equal to the stoichiometric air-fuel ratio.

Abstract: An electronic control system for a carburetor of an internal combustion engine having an induction passage, engine cooling water and a device supplies an air-fuel mixture to the induction passage. A converter converts the temperature of the engine cooling water to a first voltage signal. A choke valve is disposed in the induction passage and a bimetal actuates the choke valve. A positive temperature coefficient heater heats the bimetal. A heater circuit produces a second voltage signal dependent on the resistance of the positive temperature coefficient heater. An air-fuel ratio controller controls the air-fuel ratio of the mixture supplied by the air-fuel mixture supply device. A calculating circuit combines the voltage signals from the converter and the heater circuit respectively and produces an electronic control for controlling the air-fuel ratio control.

Abstract: An electronic control system for a carburetor of an internal combustion engine for controlling the air-fuel ratio to a value providing satisfactory cold engine operating performance. The system comprises an automatic choke device having a heater operative in response to the temperature of the device to close the choke valve, an oxygen sensor for detecting the content of the exhaust gases, an air-fuel ratio controlling means, and an electronic control means selectively operative to the signals from the oxygen sensor and the automatic choke device. The heater of the automatic choke device is a PTC heater, the resistance of which increases with the increase of the temperature thereof. The air-fuel ratio control means comprises an electromagnetic valve for controlling the fuel supply or air flow rate.

Abstract: A system for controlling the air-fuel ratio for an internal combustion engine having an induction passage, an exhaust passage, a choke valve in the induction passage, an automatic choke device comprising a positive temperature coefficient (PTC) heater and a bimetal element connected to the choke valve, a detector for detecting the concentration of a constituent of exhaust gases passing through the exhaust passage, an electronic control circuit, an on-off type electromagnetic valve actuated by the output signal from the electronic control circuit for correcting the air-fuel ratio of the air-fuel mixture supplied by an air-fuel mixture supplier, and means for actuating the on-off type electromagnetic valve at a fixed duty ratio during cold engine operation.