Originally Posted by shipjumper
I personally am having random surging / hesitations that I cannot track down... no CELs either...
I had the surging/hesitations for two days without any CEL's. After taking it to the dealer, they drove the car, and during one of their drives, the CEL came on. The dealer service mgr told me that if they had not gotten a CEL, that it would've been difficult to diagnose, and he wasn't sure how long it would've taken to properly diagnose.
So its possible that you have an O2 sensor problem, and it might be prudent to have that checked first. Apparently there is an easy way to test O2 sensors, so the dealer should be able to do it quickly. But as another person in this thread has pointed out, its possible that there is another problem that led to an O2 sensor failure.
For my car, it appears that the O2 sensor replacement did the trick, because the car runs great now, and feels stronger than it did, plus there is now a slight increase in gas mileage. For now, it appears that there are no other driveability problems with my car, so I have to conclude that the O2 sensor was indeed the problem.