bad o2 sensor?

[GooeyGus]

Hi guys,
I've been trying to track down the source of my declining fuel economy. The car seems like it just doesn't have the 'umph' that it should at part throttle / freeway cruising. At WOT it seems ok, no black smoke or anything.

So I changed my knock sensor yesterday and that solved the issue of timing being pulled. My old sensor was really really bad, but still functional (just overly sensitive)

But I still noticed that on the freeway the part throttle acceleration just doesn't feel right, and that my fuel economy is suffering because of it.

I've also been having an intermittent CEL. It will usually come on after i've been driving for about 10-20 minutes, and then go off after a few minutes.

I cant get the damn light to stay on long enough to be able to to get the codes from it though!!! (the ONE time I actually WANT my CEL to stay on and it keeps turning off.... go figure...)

So really I can only think of two things that will throw a CEL that wont severely effect how the car feels. These two things are O2 sensor and knock sensor. Seeing as how my knock sensor is brand new, my bets are on the O2 sensor.

SO... which O2 sensor should I buy?? Can I buy one from "oxygensensors.com" or should I go with an OEM sensor?

thanks!!

 

[TheAButton]

It sounds like an O2 sensor to me, but it's weird that the CEL turns off on ya. When my friends went out his light stayed on, but that's neither here nor there. We bought his from NAPA and it seemed to work just fine, it didn't look exactly like OEM though, but the data logger said everything was A Ok