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The following study was performed to investigate the in-use emissions performance of a California TLEV equipped with components aged in customer service on an enhanced I/M test. Fuels and ambient temperature conditions were chosen to compare I/M test conditions typical for California (moderate temperature on California Phase II gasoline) to those likely to be encountered in a Northeastern state (cold temperature on Winter grade fuel). To obtain repeatable results and simulate typical customer driving prior to the test, Bag II of the FTP schedule was used to simulate urban driving to an I/M lane, followed by a variable length idle to simulate waiting for the I/M test, followed by the IM240 test.

Three vehicle and dynamometer-aged converters were evaluated for performance using the warmed-up portion (termed the “hot-18” cycles) of the Federal Test Procedure (FTP) and during a steady-state cruise using low and high sulfur content fuel. During the steady-state tests the catalyst performance was also monitored using two oxygen sensors designed to satisfy Phase II On-Board Diagnostics (OBD-II) requirements for vehicles sold in California in MY 1994 and thereafter. The performance of two of the converters decreased significantly upon switching to the high sulfur content fuel, and one of the converters which was diagnosed as passing with low sulfur fuel was diagnosed as failing with high sulfur fuel.