It appears that I am getting low voltage readings from all four O2 sensors on my 98 Z28 A4. I had Autozone do a scan and received the following: PO131, PO137, PO151, PO157. I really doubt all 4 O2 sensors are bad. But maybe. I have had this issue ever since I bought the car a month ago. The SES light is on a majority of the time, but not always.

Any ideas on what causes it to run lean? I have noticed that it does runs little rough and does not seem to be as fast as I would expect from an LS1.
Thanks for any ideas on what to check.

 

if its running bad then it prob is the o2s that are bad

 

Could it possibly be a bad fuel filter??? Thanks.

 

i wouldnt worry about the fuel filter, esp if you are getting o2 codes. check the oscillation on them first