O2 sensors at WOT?

[Bill the arcstarter]

List,
 I've heard that most ECU's go into an open-loop condition while under 
WOT.  I've also heard this is because most O2 sensors read incorrectly 
under WOT conditions.

Why is that?  Does the increased gas flow cool the O2 sensor down too 
much or what?

Is the decision by the ECU to go open loop - based on TPS alone or on 
(what) else??

Someone else said that a heated O2 sensor will respond to hydrocarbon 
levels if it is not warmed up properly.  If this is true perhaps a poor 
man's gas analyzer could be constructed using one heated (to measure O2) 
and one unheated to measure hydrocarbons, etc???

Thanks!
-Bill

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