CONVERTER EFFICIENCY CHARTS:
Converters can only work efficiently if the engine is operating properly and the exhaust is leak tight. The charts at below show the typical relationship of engine exhaust, converter efficiency and resulting tailpipe emissions measured during emission tests. Both too-
rich or too-lean conditions can cause emission failures.
| HC |
CO |
NOx |
Possible Cause or Recommended Action |
| High |
High |
High |
Replace converter and O2 sensor;
verify tune-up and correct any faults |
| High |
Low |
High |
Replace converter, tune-up & check lean
AFR, leaking exhaust valves |
| Low |
High |
High |
RReplace converter and O2 sensor |
| High |
High |
Low |
Rich AFR, air injection |
| High |
Low |
Low |
Run-in converter, tune-up, oil change |
| Low |
Low |
High |
EGR, lean AFR, leaks, run-in converter,
use larger converter |
| Low |
High |
Low |
O2 sensor, rich AFR |
|
Low means less than the test fail point;
high means near or above the test fail point.
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