Abstract: In a double air-fuel ratio sensor system having three-way catalysts, a full O.sub.2 storage amount of the three-way catalysts is estimated and compared with a predetermined amount. When the estimated full O.sub.2 storage amount is smaller than the predetermined amount, the three-way catalysts are determined to have deteriorated.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side air-fuel ratio sensor and the downstream-side air-fuel ratio sensor. The adjustment of the air-fuel ratio by the downstream-side air-fuel ratio sensor is stopped when the engine is in a predetermined state.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, a delay operation is performed upon the output of the downstream-side air-fuel ratio sensor, so that the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side air-fuel ratio sensor and the delayed output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is gradually changed in accordance with the output of the upstream-side air-fuel ratio sensor, and the actual air-fuel ratio is adjusted in accordance with the air-fuel ratio correction amount. The gradual-change speed of the air-fuel ratio correction amount is changed in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is remarkably changed when the output of the upstream-side air-fuel ratio sensor is switched from the lean side to the rich side or vice versa, and the actual air-fuel ratio is adjusted in accordance with the air-fuel ratio correction amount. The remarkable-change speed of the air-fuel ratio correction amount is changed in accordance with the output of the downstream-side air-fuel ratio sensor.

Abstract: In a method of controlling the restart of an engine wherein the fuel amount is increased to prevent a restart failure of the engine from occurring at the time of the restart at high temperature, a fuel pressure is raised, a fuel amount is increased, an idling speed is raised and an idle ignition timing is advanced when the temperature of the engine is higher than a preset temperature and it is within a preset time period after the start of the engine, whereby the fuel consumption performance and the idling stabilizing performance are improved.

Abstract: An internal combustion engine has several cylinders. A construction is provided for the intake system of the engine, including a surge tank with an inlet through which air is admitted, and one intake tube for each cylinder. Each of the intake tubes is defined by a wall, and leads from the surge tank to its cylinder. An upstream part of each intake tube is wrapped around the surge tank and extends along its wall. Desirably, the wall of this wrapped upstream part of each intake tube may in part be constituted by the outer part of the wall of the surge tank. A part of each intake tube downstream of this wrapped upstream part may be wrapped along the wrapped upstream part.

Abstract: Fuel is cut off in the deceleration of a vehicle to improve efficiency of fuel consumption. Rotational speed of an engine in the resumption of fuel supply in the completion of the fuel cut-off is set to a value smaller than that otherwise set when a brake device is operated or the vehicle speed is higher than a predetermined value. While the torque of the engine varies abruptly to produce impact when the fuel cut-off is completed, passengers have a slight feeling of impact while the vehicle is being braked and travelling with high speed. Thus, while the feeling of impact is reduced, a period of fuel cut-off is increased to improve further the efficiency of fuel consumption and others.

Abstract: Disclosed is a device for promoting the purification of exhaust gas in an internal combustion engine at the time of warm-up. The opening degree of the throttle valve of the carburetor is temporarily maintained open at about 20 degrees immediately after the engine is started. After this, the throttle valve is closed stepwise to its idling position as the temperature of the engine is increased. When the gear shift of the transmission is shifted from neutral to, for example, low gear, for driving a vehicle in the case wherein the opening degree of the throttle valve is being held open at about 20 degrees, the throttle valve is automatically closed to an opening degree which is smaller than 20 degrees.

Abstract: Disclosed is an internal combustion engine provided with an exhaust gas recirculation system for recirculating exhaust gas from at least one but not all of the combustion chambers into an intake manifold. This internal combustion engine is also provided with an air injection system for introducing an appropriate amount of secondary air necessary for maintaining an effective exhaust gas recirculation operation. Means are provided for introducing an excessive amount of secondary air into the exhaust system at positions located near the combustion chambers including the chamber from which exhaust gas is recirculated, when the engine is operating under a warming-up condition. Accordingly, a catalytic converter located downstream of the exhaust manifold is rapidly activated just after the starting of the cold engine for oxidizing CO and HC components in the exhaust manifold.

Abstract: A catalyst container for use in an exhaust manifold, which container includes perforated inner and outer cylinders and is positioned within the exhaust manifold, in the position of its exit, with catalysts filled in a cylindrical space defined between the inner cylinder and outer cylinder. In this catalyst container, annular openings in the cylindrical space at its top and bottom ends are covered with annular upper and lower lids, respectively, while a circular, inner cylinder lid is placed over the top opening of the inner cylinder to cover it. In addition, an outer cylinder lid is placed on the top circumferential edge of the outer cylinder in a manner to cover the top opening of the outer cylinder as well as the circular, inner cylinder lid. The catalysts are filled in a first space defined by the inner cylinder lid and the outer cylinder lid as well as in a second space defined between the outer cylinder and the inner cylinder.

Abstract: An internal combustion engine exhaust manifold with cylindrical built-in catalyst container which comprises cylindrical inner and outer cylinders and annular lids fitting at opposite ends thereof and is filled with a catalyst suitable for cleaning the engine exhaust.An exhaust gas cleaning device using the exhaust manifold comprises an oxygen concentration sensor located in the exhaust gas flow and an electronic fuel injector for performing feedback control in accordance with a signal from the oxygen concentration sensor.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.