CIS experts-The winner

[JanDebL at aol.com]

"The problem is that when cold, or not under throttle for that matter, the O2 
is not heated and the ECU overcompensates thinking things are going lean, 
which results in a totally rich mixture! " 

I question the O2 sensor pre-heat theory.  The preheat only helps during 
engine warmup - the older O2 sensors had to wait for until they were warmed 
by the exhaust to work properly.  But once the sensor is warm (either by the 
internal heating element or the exhaust gases) the sensor should function 
properly.
Just my O2 cents
Jan Lahtonen