Emission Control Systems

Operation of the Catalytic Converter

Key Concepts

1. An air/fuel mixture of 14.7:1 is the best compromise, but it does not provide perfect combustion. 2. A 14.7:1 mixture gives the lowest CO and HC levels, but it also produces very high NOx levels. 3. A 3. 14.7:1 mixture also results in low oxygen levels.

Misfire

Single cylinder misfires are completely ignored by the traditional 5-gas graph. Partial misfires that are not related to an overall lean condition are also ignored. The following chart can be very useful in helping to identify single cylinder misfires and partial misfires.