An Evaluation of Restorative Maintenance on Exhaust Emissions from In-Use Automobiles

This paper describes the results of an automobile exhaust emission testing program conducted by the U.S. Environmental Protection Agency. A total of 381 vehicles were subjected to a series of tests before and after various stages of tune-up. The vehicles were low-mileage 1975, 1976, and 1977 models of the three major domestic manufacturers and were obtained from private owners. Significant findings include the confirmation of the poor emission performance of newer vehicles when compared to their standards, the wide extent of maladjustments and disablements and the large emission reductions possible upon correction of these problems.