INTAKE AIR ABNORMALITY DIAGNOSTIC DEVICE

PROBLEM TO BE SOLVED: To provide an intake air abnormality diagnostic device capable of diagnosing the presence or absence of failure of a mechanism for adjusting intake air flow rate of combustion air highly reliably with a simple structure.SOLUTION: An engine control device 20 for diagnosing the presence or absence of the occurrence of abnormality of an intake air adjusting device (TCV) which adjusts intake air flow rate of gas mixture introduced into a combustion chamber of an engine includes: a state checking part 21 which checking that the engine comes to a preset driving state and is during diagnostic period; a diagnostic time measuring part 22 which measures a duration time of the diagnostic period; a knock sensor 39 which detects knocking of the engine; a knock count part 23 which counts the number of times of knocking detection during the diagnostic period; and a failure determining part 24 which determines that the abnormality occurs in the TCV and determines that a fault occurs when the number of times of detection during diagnosis duration period gets to a preset determination threshold or more.