Methods and systems include determining a cylinder air-fuel ratio imbalance in a multi-cylinder engine. In one example, the method may include sequentially firing an engine cylinder to provide an expected air-fuel deviation and learning cylinder air-fuel ratio imbalance based on an error between an actual air-fuel ratio deviation from a maximum lean air-fuel ratio relative to an expected air-fuel deviation during a deceleration fuel shut-off event.

Methods and systems are provided for reducing accumulation of condensate in an engine intake during an engine non-combusting condition. In one example, during an engine non-combusting condition, responsive to a higher than threshold ambient humidity and a lower than threshold intake manifold temperature, intake and exhaust valves of deactivatable cylinders may be closed in order to seal the cylinders and during an immediately subsequent engine combusting condition, the intake and exhaust valves of the deactivatable cylinders may be activated and combustion may be resumed in the deactivatable cylinders before starting combustion in non-deactivatable cylinders. Also, during the engine non-combusting condition, residual hot exhaust may be recirculated to the intake manifold to evaporate condensate in the intake manifold.

Systems and methods for determining operation of a cylinder deactivating/reactivating device are disclosed. In one example, a warm engine is rotated without being supplied fuel to determine the presence or absence of valve actuator degradation. Degraded valve actuators may be determined when there is a lack of a temperature rise in the engine exhaust system.

A control device is applied for an internal combustion engine which is provided with a high-pressure fuel pump driven by a driving shaft of the internal combustion engine to discharge a fuel pressurized in a pressurizing chamber, an accumulator accumulating a high-pressure fuel discharged from the high-pressure fuel pump, and a relief valve which is opened when a fuel pressure in the accumulator is higher than a specified pressure in order to return the fuel in the accumulator to a specified chamber where a fuel has lower pressure than a fuel in the pressurizing chamber. An idle speed of the internal combustion engine is increased to a specified speed when the fuel pressure in the accumulator has been higher than a determination pressure, which is lower than the specified pressure, for a first period or longer.

System comprising an internal combustion engine including a crankshaft, a crankshaft sprocket coupled to the crankshaft, an electric motor in mechanical communication with the crankshaft sprocket, a bidirectional engine position sensor coupled to the crankshaft sprocket, a controller in electrical communication with the bidirectional engine position sensor and a non-transitory memory having instructions that, in response to execution by a processor, cause the processor to determine a position of an engine component upon shutdown of the engine, store the position of the engine component at shutdown in the non-transitory memory, and control the electric motor at restart in response to the position of the engine component at shutdown are disclosed. Methods are also disclosed.

Systems and methods for diagnosing the presence or absence of turbocharger wastegate degradation are presented. In one example, an intake manifold pressure sensor provides a basis for determining whether or not turbocharger wastegate degradation present. The turbocharged engine may be rotated in a reverse direction to assess wastegate degradation.

Methods and systems are provided for diagnosing degradation of an exhaust gas recirculation (EGR) valve. In one example, a method may include, during a vehicle key-off condition, routing compressed air through an EGR passage housing the EGR valve, and indicating degradation of the EGR valve based on a change in an estimated EGR pressure, upon a commanded change in EGR valve position.

Methods and systems are provided for diagnosing the functioning of a variable displacement oil pump. In one example, a method may include commanding a change in displacement of the variable displacement oil pump during a vehicle keyed-off condition and diagnosing a degradation of the oil pump based on a corresponding change in an estimated crankcase pressure.

Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, the engine system may be installed in a hybrid vehicle, and, in response to a request to restart the engine while the vehicle is being propelled via motor torque only, the engine may be rotated unfueled via the motor torque at less than cranking speed while at least partially opening a valve disposed in a passage coupled between the first exhaust manifold and the intake passage. In another example, in response to the request to restart the engine, all exhaust valves of a second set of exhaust valves coupled to the second exhaust manifold may be deactivated.

There is provided a hybrid vehicle comprising a mode selection device configured to select one drive mode among a plurality of drive modes according to a user's operation. The plurality of drive modes include a first drive mode in which the hybrid vehicle is driven with power from a motor with stopping rotation of an engine and a second drive mode in which the hybrid vehicle is driven with rotation of the engine. On satisfaction of filter regeneration conditions that an accumulated amount of particulate matter accumulated on a filter is equal to or greater than a predetermined accumulated amount and that a temperature of the filter is equal to or higher than a predetermined temperature, the hybrid vehicle is driven in the second drive mode even when the first drive mode is selected by the mode selection device.