Abstract: In an engine device driven by gaseous fuel, abnormal combustion occurring in a combustion chamber of an engine is detected, an occurrence frequency and an occurrence intensity of the abnormal combustion are monitored, and a suppression method for suppressing the abnormal combustion is determined according to the occurrence frequency and the occurrence intensity. At least one of ignition timing of the gaseous fuel, an air excess ratio of intake air in a mixture gas composed of the gaseous fuel and the intake air, and shut-off of the gaseous fuel is controlled as the suppression method in the engine device.

Abstract: A diagnosis device for a multi-cylinder internal combustion engine having an exhaust turbocharger, the device configured to diagnose a fuel combustion state in each one of cylinders in the internal combustion engine. The diagnosis device includes: a rotational speed detector configured to output a signal corresponding to a rotational speed of the exhaust turbocharger or a signal correlated to fluctuation in the rotational speed of the exhaust turbocharger, and a fuel combustion state diagnosis unit configured to diagnose unevenness in the fuel combustion states of the cylinders through a frequency analysis involving a fast Fourier transformation of a frequency characteristic of a signal output from the rotational speed detector.