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As part of the Auto/Oil Air Quality Improvement Research Program (AQIRP), a fleet of 299 1983-1993 “real world” light duty vehicles and trucks were acquired from inspection and maintenance (I/M) lanes and tested at prevailing ambient temperatures for their hot soak emissions for the first hour after the engine was turned off. When found, high-emitters were repaired and retested to quantify the effectiveness of the repairs. Also, I/M pressure-purge tests were performed to determine whether such tests could properly identify high-emitting vehicles. Measured hot soak emissions ranged from less than 0.1g HC to as high as 49g HC. Twenty percent of the vehicles tested accounted for nearly 80 percent of the total hot soak emissions, with no single common hardware component identified as the primary cause.

The E-35 “Running Loss” program was planned in the fall of 1996, and conducted in the summer of 1997, as the third part of a series of Coordinating Research Council (CRC) sponsored evaporative emission test programs. One hundred and fifty vehicles (half cars - half light duty trucks) were recruited at a local I/M lane, and tested for running loss emissions at the ATL Facility in Mesa, AZ. The previous CRC programs had studied hot soak, and then diurnal emissions. Running loss emissions were measured in a Running Loss SHED (RL-SHED) for a 25 minute, 7.5 mile trip on a hot summer day (95°F). Vehicles from model years 1971 through 1991 were tested. A wide range in emission levels was observed - from a low of 0.13 g/mile to 43 g/mile. The test results were not able to establish whether car emissions are different, or the same, as light duty trucks. The major causes of the high emissions were liquid leaks on carburetor equipped models.