The tow pig, an 04 silverado with a 4.8 has been a little down on power and MPG this year. Carrying 1000# payload and pulling 3500#. Not a lot, but every pony makes a difference. I changed the air filter even though it looked good. Plugs are 3 years old, about 30K miles. O2 sensors unknown. Plugs are cheap, should I do the O2 sensors also?
Quick google reveals numbers all over the place, from 30k to 100k miles. Since most of these places are trying to sell O2 sensors, I'd use the 100k mile number.
You can look at fuel trims with a scanner. If they are different bank to bank likely one is starting to get goofy. They aren't expensive to do and just did a pair on my 6.0 due to one going bad at 198k.
In reply to Paul_VR6 (Forum Supporter) :
Just as important, when you are scanning them, you can look at the responsiveness of the sensor. If they don't move, it's a good chance they are dead (although on an 01, that will light the MIL light).
Their life is also highly dependent on their quality. Cheap aftermarket sensors last long enough to sell it without the CEL coming on. OEM sensors seem to last forever. Most I got out of a pair of upstreams was 340k in an F150, and I sold it, so for all I know they're still going strong
The vehicle is new enough that if a sensor were getting lazy or skewed, it would set a fault code.
Because of Murphy's Law, when the upstream sensor gets skewed, it assumes that the REAR sensor is bad...
I'd be more inclined to believe that the brakes are dragging, or the alignment is off, or the exhaust is starting to break up internally.
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