An exhaust gas control apparatus for an internal combustion engine includes: a catalyst disposed in an exhaust passage of the engine and configured to be able to occlude oxygen; an air-fuel ratio sensor that detects an air-fuel ratio of an out-flow exhaust gas; and an air-fuel ratio control device that controls an air-fuel ratio of an in-flow exhaust gas to a target air-fuel ratio. The device executes air-fuel ratio reduction control in which the target air-fuel ratio is set to a rich setting air-fuel ratio, and corrects a parameter related to the air-fuel ratio reduction control such that an amount of a reducing gas supplied to the catalyst is decreased when a minimum air-fuel ratio obtained when the detected air-fuel ratio is varied to a rich side is richer than the rich setting air-fuel ratio or an average value of detected air-fuel ratios of the in-flow exhaust gas.

When a performance flag of a temperature raising process becomes “1”, a CPU increases an injection amount for first, third and fourth cylinders from a base injection amount for making an air-fuel ratio of an air-fuel mixture equal to a theoretical air-fuel ratio, by an increase amount, and stops combustion control in a second cylinder. The CPU gradually increases a ratio of the increase amount to the base injection amount, at the start of the temperature raising process.

A controller for an internal combustion engine includes processing circuitry that executes a richening process until an exhaust sensor detects exhaust gas having a rich air-fuel ratio. The processing circuitry executes an air supplying process to supply a catalytic converter with air until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio. The processing circuitry cumulates the amount of air supplied to the catalytic converter until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio in the air supplying process. The air supplying process includes stopping fuel supplied to the one or more of the cylinders and performing combustion at an air-fuel ratio that is less than or equal to the stoichiometric air-fuel ratio in the remaining one or more of the cylinders.

Methods and systems for increasing exhaust gas temperatures of an engine are described. In one example, engine exhaust gas temperatures may be increased via deactivating cylinders and flowing exhaust gases through deactivated cylinder. Engine pumping losses may be reduced via the exhaust gases that flow through the deactivated cylinder so as to reduce engine fuel consumption while heating an exhaust gas after treatment device.

A control device is capable of executing: an ignition time calculation process of calculating a target ignition time of an ignition plug; a stop process of stopping combustion control for some cylinders of a plurality of cylinders; and a compensation process of controlling a motor generator during the stop process, such that the motor generator compensates a drive power that is lost due to the stop of the combustion control. The control device prohibits the execution of the stop process when the target ignition time calculated in the ignition time calculation process is on a retard side of a predetermined prescribed time.

A system and method for the use of machine learning for detecting faults for cylinder intake and/or exhaust valves that do not properly open or close as commanded and for generating a flag for such faults.

A controller for an internal combustion engine includes processing circuitry that executes a richening process until an exhaust sensor detects exhaust gas having a rich air-fuel ratio. The processing circuitry executes an air supplying process to supply a catalytic converter with air until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio. The processing circuitry cumulates the amount of air supplied to the catalytic converter until the exhaust sensor detects that the exhaust gas has a lean air-fuel ratio in the air supplying process. The air supplying process includes stopping fuel supplied to the one or more of the cylinders and performing combustion at an air-fuel ratio that is less than or equal to the stoichiometric air-fuel ratio in the remaining one or more of the cylinders.

A system and method for a variable displacement internal combustion engine using different types of pneumatic cylinder springs on skipped working cycles to control engine and aftertreatment system temperatures are described. The system and method may be used to rapidly heat up the aftertreatment system(s) and/or an engine block of the engine following a cold start by using one or more different types of pneumatic cylinder springs during skipped firing opportunities. By rapidly heating the aftertreatment system(s) and/or engine block, noxious emissions such as hydrocarbons, carbon monoxide, NO.sub.x and/or particulates, following cold starts are significantly reduced.

A controller for a hybrid vehicle controls an electric motor such that a motor torque is input to a crankshaft in order to compensate for a decrease in an engine torque when a cylinder deactivation control is executed, the decrease resulting from suspension of combustion in one or some of cylinders. The controller calculates an engine torque calculated value using an engine rotation speed, a motor rotation speed, and the motor torque. The controller diagnoses that the cylinder deactivation control is functioning normally when the engine torque calculated value is less than a torque determination value and diagnose that the cylinder deactivation control is not functioning normally when the engine torque calculated value is not less than the torque determination value during the execution of the cylinder deactivation control.

A system and method for a variable displacement internal combustion engine using different types of pneumatic cylinder springs on skipped working cycles to control engine and aftertreatment system temperatures are described. The system and method may be used to rapidly heat up the aftertreatment system(s) and/or an engine block of the engine following a cold start by using one or more different types of pneumatic cylinder springs during skipped firing opportunities. By rapidly heating the aftertreatment system(s) and/or engine block, noxious emissions such as hydrocarbons, carbon monoxide, NO.sub.x and/or particulates, following cold starts are significantly reduced.