A control for an internal combustion engine makes an air-fuel ratio in at least one of a plurality of cylinders equal to a rich air-fuel ratio smaller than a theoretical air-fuel ratio, makes an air-fuel ratio in each of the other remaining ones of the plurality of the cylinders equal to a lean air-fuel ratio larger than the theoretical air-fuel ratio, executes a temperature raising process for raising a temperature of a catalyst that purifies exhaust gas from the plurality of the cylinders, executes a detection process for detecting a degree of dispersion of the air-fuel ratio among the plurality of the cylinders, and executes a determination process for determining, based on the detected degree of dispersion, whether or not a plurality of fuel injection valves corresponding to the plurality of the cylinders respectively are normal, and executes the detection process while avoiding a period of the temperature raising process.

An internal combustion engine includes a variable mechanism that changes a working angle of an intake valve. A controller diagnoses whether there is an abnormality that an intake air amount reduces during idle operation. The controller changes an abnormality determination threshold for diagnosing an abnormality on the basis of a mode in which the working angle is changed by the variable mechanism.

A piezo-driven fuel injector is modeled by measuring the actuation current and the actuation voltage of the piezo injector, transforming the actuation current and the actuation voltage into the frequency domain, forming a complex conductance from the actuation current transformed into the frequency domain and the actuation voltage transformed into the frequency domain, and determining one or more parameters of the piezo injector from the complex conductance. Once the complex conductance is determined it is used to detect a fault in the piezo injector.

A method and a system for detection of torque deviations of an engine (101) in a vehicle (100). A measurement (201) is made of actual measured values D.sub.act related to a behavior of at least one parameter which is related to an actual torque M.sub.eng.sub._.sub.act delivered by the engine (101). This actual torque M.sub.eng.sub._.sub.act is delivered here by the engine (101) in consequence of a torque M.sub.eng.sub._.sub.req demanded from the engine (101). A comparison (202) is then made of the actual measured values D.sub.act which are related to the behavior of the at least one parameter with previously determined measured values D.sub.ref of correspondingly at least one respective parameter related to the actual torque M.sub.eng.sub._.sub.act. The previously determined measured values D.sub.ref will here have been determined during normal operation of the vehicle (100). Detection is then made of whether the actual measured actual torque M.sub.eng.sub._.sub.act deviates from the demanded torque M.sub.engj-eq. The detection is based here on the comparison of the actual measured values D.sub.act with the previously determined measured values D.sub.ref.

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, all intake valves of an engine cylinder may be deactivated, in response to engine load below a threshold, while operating a first exhaust valve coupled to the first exhaust manifold and a second exhaust valve coupled to the second exhaust manifold at different timings. As a result, intake air may be routed from the intake passage, through an exhaust gas recirculation passage coupled between the intake passage and the first exhaust manifold, and into the engine cylinder via the first exhaust valve.

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, exhaust from a first set of exhaust valves coupled to the first exhaust manifold may be selectively routed to the intake passage via each of a first EGR passage coupled to the intake passage upstream of a compressor driven by a turbine and a second EGR passage coupled downstream of an outlet of the compressor. A decision of whether to route exhaust gas to the intake passage via the first EGR passage, second EGR passage, or both passages may be based on engine operating conditions.

Methods and systems are provided for reducing lean air-fuel ratio excursions due to degradation of a port injector while fueling an engine via each of port and direct injection. During a PFDI mode of engine operation, responsive to an indication of port injector degradation, such as due to circuit or injector power issues, intake airflow is limited by reducing the opening of an intake throttle. Air flow is limited to be based only on the direct injected fuel fraction, and independent of the commanded port injected fuel fraction.

An engine control apparatus and method in which when an injector malfunction is determined based on a difference in variation of angular velocity of a crankshaft between a plurality of cylinders of a vehicle engine, determining whether the injector malfunctions by avoiding the time when the driving torque of an air compressor is applied or at the time when the influence thereof is reduced, thereby preventing the erroneous determination of whether the injector malfunctions from occurring due to the driving torque of the air compressor connected to the vehicle engine.

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, a first set of exhaust valves coupled to the first exhaust manifold may be operated at a different timing than a second set of exhaust valves coupled to the second exhaust manifold. Further, a position of a first valve positioned in a first passage coupled between the intake passage and the first exhaust manifold and/or a timing of the first set of exhaust valves may be diagnosed based on an output of a pressure sensor positioned in the first exhaust manifold.

An internal combustion engine includes a cam-actuated rocker arm assembly with a solenoid-actuated latch that provides for cylinder deactivation or variable valve actuation. The solenoid is in a position where its inductance varies significantly in relation to the position of a latch pin as it translates between latching and non-latching configurations. A sensor is positioned to monitor a current or a voltage in a circuit that includes the solenoid. The sensor data is analyzed to provide diagnostic information relating to the operation of the rocker arm assembly.