why would an O2 sensor be out of the loop when the engine is cold?

If it is left in the loop it will lean out the mixture when the engine is cold and needs the extra fuel to run..
The computer keeps the mixture a bit rich..just like the choke on a carb.. until temp is reached and then the 02 is brought into the loop to keep the milage up.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

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