The Inspection and Maintenance (I/M) Evaluation Task consisted of a series of emission and fuel economy tests on a sample of 1977 and 1978 passenger cars and thirty 1975-1978 model-year, light-duty trucks. This work was performed as an additional effort in the Denver portion of the EPA's FY77 Passenger Car Emission Factor Program. Tests were performed on the vehicles in their as-received condition. Many of these vehicles that failed an idle test during the initial test sequence were delivered to one of ten pre-selected repair and tune-up facilities in the east Denver area for corrective maintenance. Idle emission tests and maintenance actions were performed at the repair facilities before the vehicles were returned to the laboratory. These were followed by another series of tests at the laboratory to provide information on the effectiveness of the work performed. Two other tests were performed as part of the I/M program. An Induced Malperformance Idle Test, conducted with one spark plug disconnected, was performed on all the 1977 and 1978 passenger cars, all trucks and a sampling of 1975 and 1976 passenger cars. Thirty additional 1975 and 1976 model-year cars were also given a series of tests to evaluate the emission related performance of catalytic converters on vehicles with more than 50,000 accumulated miles.