| 摘要 |
PURPOSE:To surely perform failure diagnosis of an exhaust gas recirculating device without causing engine stalling nor giving a feeling of physical disorder to a driver. CONSTITUTION:When a failure diagnostic condition is realized, an exhaust gas recirculation (EGR) valve 13 is opened to simultaneously increase an amount of air of passing through a bypass passage 7 of bypassing a throttle valve 4. Here in the case of an EGR device being normal, an engine speed tends to decrease by X due to introduction of exhaust gas, but the engine speed is increased by Y due to the increased air amount, so that, as a result, an operative condition is not changed from a normal condition. On the other hand, in the case of failure a relationship where Y>X is obtained to increase a degree of rising in the engine speed. Then by detecting the degree of rising, failure in the EGR device is judged. |
