As a new concept of misfire detection, monitoring the signal variation of a wide range oxygen sensor was introduced. The misfire can be occurred not only by a lack of ignition but also by a lack of fueling and, in the case of fuel starvation, the partial burn also can be occurred. In this study, the possibility for the detection of a misfire or a partial burn caused by a lack of fueling was investigated, when a wide-range oxygen sensor was used for the misfire detection. To investigate the signal fluctuation of the wide range oxygen sensor under a misfiring or a partial burn condition, the effect of the hydrocarbon concentration on the signal output of the sensor was investigated first at steady state condition. And the signal fluctuation of the sensor at the confluence point was investigated. Through the tests, it was found that the misfire due to the lack of fueling can be detected more easily than that by a lack of ignition and that a partial burn also can be distinguished from a misfiring or a lean combustion.