o2 voltage help

[Devilsfutbol17]

I have a data logger and my o2 volts seem normal while driving, shooting all around up and down. But when at WOT it drops to .00 or .02. From what I have found, at WOT the o2 volts should be in the upper 25%. So I'm guessing that something is not right. But I haven't got and check engine lights. I have put 250 miles on my car since I have bought it and I havent got any CEL. I have a 1990 Tsi AWD and I only got 250 miles on a full tank of gas, so I'm thinking the o2 sensor is messing up my gas mileage. Any help is appreciated. Thanks

 

[spyderturbo007]

What do you mean by "shooting all around up and down". The O2 voltage should cycle around 0.50v at idle and cruise. Somewhere between 0.20v and 0.80v is normal. Can you post a log of what the O2 voltage does at idle? That would help. But you WOT reading should be somewhere around 0.90v, not 0.0v.

If I had to guess without seeing the log, I would say that your front O2 is shot. You can get them cheap from www.sparkplugs.com