John

Since you never stated the other emissions ( aside from CO, HC & Lambda ), I can only offer you some numbers that would represent an " ideal world ".

CO % after cat. conv. = 0.0 - 0.2 %
HC ppm " " = 20 - 100 PPM
O 2 % " " = 0.5 - 1.5 %
CO 2 % " " = 11 - 13 %
NOx ppm " " = 20 - 150 ppm

They are all inter-related.
Generally speaking they would be categorized in this manner:

High CO = too much fuel
High HC = ignition or mechanical problem ( oil consumption )
High NOx = EGR not working
High O2 = lean fuel mixture or misfire
There is really no such thing as high CO2, as that is primarily a measure of combustion efficiency.

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2007 C 230 Sport.