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EPA has conducted investigations into the effects on emission levels and internal catalyst temperatures versus ignition-induced misfire. These data were obtained on a 1990 Buick LeSabre. These data indicate that: (1) a two percent misfire rate was sufficient to cause hydrocarbon (HC) emission levels to exceed the existing emission standard of 0.41 gm/mile; (2) a four to five percent ignition-induced misfire rate caused the HC emission levels to reach 0.82 gm/mile, or twice the standard, (3) typical FTP average internal catalyst temperatures are below 514°C; and (4) maximum internal catalyst temperatures were below the threshold temperature for thermal degradation (870°C) during ignition-induced misfire below 17 percent.

Simple tests were performed to investigate the operating characteristics of zirconia galvanic cells (lambda sensors) in automotive closed loop “three-way” emission control systems. Commercially available cells were exposed to typical gaseous components of exhaust gas mixtures. The voltages generated by the cells were at their maximum values when hydrogen, and, in some instances, carbon monoxide, was available for reaction with atmospheric oxygen that migrated through the cells' ceramic thimbles in ionic form. This dependence of galvanic activity on the availability of these particular reducing agents indicated that the cells were voltaic devices which operated as oxidation/reduction reaction cells, rather than simple oxygen concentration cells.