Systems for evaluating possible abnormality in an engine

Embodiments of the present invention may include a system for evaluating a possible abnormality in an engine (2). The system includes an engine (2), an EGR passage (4, 5) and an ECU (6). The rotational speed of the engine (2) is preferably calculated based on a crank angle. The ECU (6) preferably calculates a flow rate of gas in an engine (2) cylinder based on the rotational speed of the engine (2), a temperature detected by a temperature sensor (12a) and a pressure detected by a pressure sensor (12b). The ECU (6) calculates a flow rate of the EGR gas on basis of a differential pressure between an upstream and a downstream of an EGR valve (32, 42) and an degree of opening of the EGR valve (32, 42). The ECU (6) calculates a difference between a reference value of a flow rate of a new gas and a detection value of the flow rate of a new gas. The reference value is obtained by subtracting the calculated flow rate of the EGR gas from the calculated flow rate of the cylinder flowing gas. The detection value is detected by an air flow meter (16). The ECU (6) judges whether the air flow meter (16) is acting abnormally when the difference between a reference value of a flow rate of a new gas is equal to or more than a predetermined value.