Device for detecting abnormality in an engine intake system

A calculation intake air amount GP is calculated on the basis of an intake air pressure Pim detected by a pressure sensor and an intake air temperature Tim detected by a temperature sensor, and an actual intake air amount GF is detected by an air flow meter. A temporary abnormality judgment is made as to whether the value obtained by subtracting the actual intake air amount GF from the calculation intake air amount GP, i.e., GP - GF, is larger than a predetermined value alpha . When the condition of the temporary abnormality judgment is satisfied continuously for a predetermined period of time, and further, repeatedly a predetermined number of times, it is determined that there is some abnormality in the intake system.