I ran diagnostics on my 305 TBI, and had no logged fault or event codes, but in closed loop, I was bouncing back and forth between lean and rich mixture while idling, even after she was warmed up good.........Checked this because I have been burning alot of gas in my 91 'Bird....... Only getting about 220 miles on a full tank of gas.....Seems i'm burning alot only when at 65+ mph. Should I look at replacing my O2 sensor, or any recommendations/ comments?
Thanks in advance..

 

It is normal for your 02 volts to bounce a round a bit. They should stay steady when you go WOT. When was the last time the car had a good tune up. These cars tend to get neglected over time.

 

She had a tune up last summer, and she's only got 60,000 orig miles on her... Do you guys get the approx same gas mileage of about 210-220 miles per tank o' gas ?
Thanks again

 

That is not bad mileage if it is a combo of city and highway. A full tank used on the highway should yeild more miles though.

Was the 02 and plug wires replaced during that tune up?

 

I got her last summer, and the dude i bought it off of said he did the tune up, so my guess is not probable.... plugs and wires were replaced... If the O2 sensor was acting up, I'd probably pick it up as a fault logged, correct ? the solenoid air valve chech was ok, I was just concerned because it was fluctuating btwn lean and rich, but from what I remember, the o2 sensor voltage was fluctuating btwn a decent range....

 

If you replace your 02 you want to go with a delco unit. A bosch one will make your car run a bit rich. Fluctuating 02 volts is normal. I would replace the 02 if it looks like it is an origonal.

 

O2 sensors can go bad without throwing codes. I've already had it happen in two of my cars one got stuch reading rich and the other lean but no codes. They're cheap anyway if its original or in dout i would change it. Definately can't hurt.