Right now I am getting horrible gas milage, about 150 to a tank if Im lucky. The cruise AFRs are around 11.8-12.1 The sensor has 50k on it with a ton of race gas and methanol sprayed onto it over the years. What Im wondering is what should the front sensor read during cruise? I get about .02V during cruise. Ill have a log up here to show in a few moments

 

 

wow, you're getting a ton of knock continuously! Those AFR's definitely suggest a bad Front O2 sensor. Have you logged the frnt O2 sensor while in closed loop? It should cycle back and forth from .1 to .9 volts roughly. The resolution of that snapshot isn't good enough for the front O2 sensor readings but it sure looks F'd to me.

 

wait so a normal working front o2 at closed should range from .1-.9 correct?

 

Cruise AFR's should bounce around Stoic (14.7:1) and your narrowband 02 voltage should cycle from around .79 to .05 under idle and cruise.

I would say your front 02 is dead.

 

you should get a CEL for it thou...

 

Jea, when it doesn't occillate and don't throw a CEL it is may stuck in an open loop mode. Log also all logable sensors and check them for plausibility.

 

That was knock voltage, not counts. As far as I know it is now officially dead, in Evoscan this morning it wouldn't even read 0.001. During closed loop it will range from .10 to .41 thats the highest Ive seen it read

Tephra- Ive had a PO171 for about a year. It would come and go every week or so. I think this winter did it in. The new one is showing up today whenever UPS decides to drop it off, Ill throw up an before/after log as well when its in.