Originally Posted by 8492bird
The short answer to your question is yes. If the O2 is bad and reading lean all the time the ECM will richen the A/F mixture, causing a rich condition, in turn causing a rough idle. If the sensor has'nt been replaced in a while, go ahead and replace it.
from my understanding the o2 doesn't work all that well at idle speeds so at idle itself more or less it gets ignored until you apply a little throttle. at least with most every car I have seen it's about right. just like the O2 also gets ignored more often then not at WOT.
if you don't mind just out of curiousity is there a chance to disconnect the O2 while your car is warming up see if it runs ok afterwords.
I'm fairly sure it would still run ok but honestly I'm not 100%