I met with corvettecrazy today, he brought his cool gadget, the Autotap, I told him how i suspected my mpg was suffering sometimes and how my exhaust smells a bit too rich. So he ran autotap. Now the air/fuel ratio should be about 14.2-14.7. I got 15.1-15.4 varies but doesn't really go below 15.1. Now I suspect that'* is a bit too rich. Does that mean i need new o2 sensors? Or what?

I also told him about my theory that my fuel pump was failing (hesistating) so we tried to find the pump on autotap, but to no avail, so i need to do a fuel pressure test. But we found a fuel tank pressure, it was negative .1 to negative .2. Any one know what they mean?

Corvettecrazy will post some more numbers after he gets home. He has the program.

So come back after Corvettecrazy post the numbers then we'll all put our huge heads together.

Fuelforthesoul ~

I just posted some results of my MPG improvement in the topic "Show Me Your O2 Sensors". The improvement was almost 25% in MPG. If your O2 sensor isn't working as it should, then replacing it could have similar results.

Goos Luck!
John

The negative pressure in the fuel tank of .1 or .2 is negligible. If you see positive pressure then that would be a problem.

the numbers for while he was driving. max speed being 38ish and lowest being stopped.
these are all ranges, if you need some data from a specific rpm range or similar ask.
fuel tank preasure : -5 to 0
O2 sensor (mV)
bank 1: 50ish to 900ish
bank 2: 95ish to 700ish
they were constantly changing.

for the time of the drive, the A/F ratio was 14.7 when idling the numbers were higher as stated above.

if you need another piece of information please ask.

15.1 or so is leaner than 14.7, which is where it should be. The higher the number, the leaner the mixture.

ICE engines like 14.7 for low emissions and about 12.5:1 for max power.

You want rich? My AFR when I was dynoed was 10.2:1. I think you're doing fine fuel.

Did you guys watch the O2 sensor toggling rich lean rich lean?

A good O2 will toggle quickly.

the O2 readings are in mV. I'm guessing low voltage is one and higher is the other??

I've seen a snap on scanner and some others...

I've seen where it'* numbers like 200 then 900 back forth or rich and lean ...

Depends on your scanner...essentially ... whatever it shows you should be moving pretty quick.

Rob, is it switching back and forth quickly?