Inspection and Maintenance for 1981 and Later Model Year Passenger Cars

Inspection and Maintenance (I/M) has been demonstrated to be a practical and effective strategy for reducing the fleetwide emissions of catalyst generation and pre-catalyst generation vehicles. An issue that has been the subject of technical discussion is the need for and effectiveness of I/M for the bulk of the 1981 and later model year fleet: those vehicles equipped with closed-loop, three-way catalyst systems. This paper examines both the projected need for I/M for these vehicles as well as the effectiveness of I/M test procedures. Fuel economy considerations are also discussed.