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Subject:Re: CA SMOG, Fred's Garage, and valves
From:Bill Collins
Date:Tue, 16 Sep 2003 07:24:22 -0400
> HC levels are between 500 and 1,000 (max is
> around 200).

How is the CO level?

High CO (with or without high HC) = idle too rich

Normal CO and high HC = engine mis-firing (ignition problems?)

Low CO = Idle too lean (which can cause mis-fire, which causes high HC)

The best diagnosis is done with readings taken before the cat, but
tailpipe readings give some clues.

Bill