Patent ID: 8145412

Claim:
An internal combustion engine system having a multi-cylinder internal combustion engine that is connected to a drive shaft via a torsion element and includes an exhaust gas recirculation device which performs introduction of part of the exhaust into a gas intake line, the internal combustion engine system comprising: a rotational position detector that detects a rotational position of an output shaft of the internal combustion engine; a rotational fluctuation computation module that computes a rotational fluctuation of the output shaft at every specific rotational angle from the detected rotational position of the output shaft; and an engine misfire detection module that makes detection on occurrence or non-occurrence of a misfire in any of the cylinders of the internal combustion engine based on a first angle difference that is a difference corresponding to a first preset angle of the computed rotational fluctuations when the introduction of part of the exhaust into the gas intake line is not performed by the exhaust gas recirculation device, and makes detection on the occurrence or the non-occurrence of a misfire in any of the cylinders of the internal combustion engine based on the first angle difference and a second angle difference that is a difference corresponding to a second preset angle smaller than the first preset angle of the computed rotational fluctuations when the introduction of part of the exhaust into the gas intake line is performed by the exhaust gas recirculation device.