Emission Levels and Catalyst Temperatures as a Function of Ignition-Induced Misfire

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.