A misfire detection device for an internal combustion engine is configured to execute: a deactivating process that deactivates combustion control for air-fuel mixture in one or some of cylinders; a provisional determination process that uses a detection value of a sensor to output a logical value indicating whether a misfire has occurred; a provisional determination counting process that counts a number of times a specific one of the logical value output by the provisional determination counting process has been output; and an official determination process that makes an official determination of whether the misfire has occurred using, as an input, the number of times counted by the provisional determination counting process during a specific period.

A determination device for an internal combustion engine executes a partial fuel cut-off process. The determination device determines that exhaust gas characteristics have deteriorated when the misfire rate of the internal combustion engine is greater than or equal to a determination threshold. The determination device sets the determination threshold to a first determination threshold when the calculated misfire rate is a misfire rate in a period of non-execution of the partial fuel cut-off process. Also, the determination device sets the determination threshold to a second determination threshold, which is less than the first determination threshold, when the calculated misfire rate is a misfire rate in a period of execution of the partial fuel cut-off process.

A variety of methods and arrangements for detecting misfire and other engine-related errors are described. In one aspect, a window is assigned to a target firing opportunity for a target working chamber. There is an attempt to fire a target working chamber during the target firing opportunity. A change in an engine parameter (e.g., crankshaft angular acceleration) is measured during the window. A model (e.g., a pressure model) is used to help determine an expected change in the engine parameter during the target firing opportunity. Based on a comparison of the expected change and the measured change in the engine parameter, a determination is made as to whether an engine error (e.g., misfire) has occurred.

A system includes an internal combustion engine having a number of cylinders, with at least one of the cylinder(s) being a primary EGR cylinder that is dedicated to provided EGR flow during at least some operating conditions. A controller is structured to control combustion conditions in the cylinders in response to one or more operating conditions associated with the engine.

Misfire detection techniques for a hybrid electric vehicle (HEV) including an internal combustion engine and an electric motor involve utilizing a crankshaft speed sensor configured to generate a crankshaft speed signal indicative of a rotational speed of a crankshaft of the engine that is coupled to the electric motor via a flywheel. The techniques also utilize a controller configured to control the electric motor to provide a vibrational response to dampen disturbances to the crankshaft, receive the crankshaft speed signal, selectively modify the crankshaft speed signal to obtain a modified crankshaft speed signal, and detect a misfire of the engine based on the modified crankshaft speed signal and a set of thresholds including at least one of a negative misfire threshold and a positive vibrational response threshold.

Methods and systems are provided for reducing a spark plug soot load and a combustion chamber soot load by controlling spark plug timing while injecting water or washer fluid. In one example, water or washer fluid is injected during a torque reduction while advancing spark timing so as to provide at least a portion of the torque reduction while opportunistically cleaning soot from the spark plug and combustion chamber. By reducing spark plug soot load, misfire occurrence is reduced, while pre-ignition occurrence is reduced by decarbonizing the combustion chamber.

Methods and systems are provided for detecting cylinder misfire in a vehicle engine via a plurality of sensors, based on dual mass flywheel (DMF) operating frequency. In response to detection of a misfire event, the misfiring cylinders may be deactivated and upon confirmation of DMF operation out of a resonant frequency range, the deactivated cylinder(s) may be sequentially reactivated.

A system and method for assessing the presence or absence of ignition coil degradation for an ignition system that includes two ignition coils for each spark plug. Ignition coil degradation may be determined without having to monitor ignition coils via specialized hardware circuitry. In one example, degradation of one or more ignition coils may be inferred from cylinder the presence or absence of cylinder misfire.

An engine includes a plurality of combustion cylinders configured to burn a fuel to power the engine, and a plurality of fuel injectors. Each of the fuel injectors is arranged to distribute fuel delivered from a fuel tank to one of the plurality of combustion cylinders. The engine also includes a controller programmed to adjust a fuel trim signal gain based on sensing exhaust flow downstream of the combustion cylinders. The controller is also programmed to monitor a cumulative misfire count for each of the plurality of combustion cylinders. The controller is further programmed to issue a prognosis message identifying a state of health of at least one of the plurality of fuel injectors in response to a fuel trim signal gain exceeding an adjustment threshold and a cumulative misfire count greater than a misfire threshold.

The objective is to provide an internal-combustion-engine controller that can diagnose, at low cost and in real time, respective combustion states of a subsidiary-chamber-type internal combustion engine. An internal-combustion-engine controller according to the present disclosure controls an internal combustion engine having a main combustion chamber and a subsidiary combustion chamber from which a combustion gas is injected into the main combustion chamber through an orifice provided between the main combustion chamber and the subsidiary combustion chamber to ignite a fuel-air mixture in the main combustion chamber; the internal-combustion-engine controller includes an ion detector that detects an ion in the in the subsidiary combustion chamber and a diagnosis and control device that controls fuel supply to the internal combustion engine and diagnoses a combustion state in the main combustion chamber or in the subsidiary combustion chamber, based on an amount of an ion detected by the ion detector.