AFM using more fuel

[-Ray-]

Charlie,
After 17k miles, I know my G8 pretty well, using my Dashhawk, and common sense.
Up to 3 weeks ago, getting 28 mpg or better was not much effort with my AFM working.
I'm now fighting to get 25, and nothing has changed.
AFM used to use Approx. 1.4-1.7 gallons of gas per hour. Now I'm over 2.2 gallons per hour. A slight incline takes my fuel to 2.7 gallons per hour while AFM is active.
What could cause this sudden increase of fuel in AFM?

Recently, monitoring my o2 sensors, I have noticed them flashing in my Dashhawk every few seconds or so. Running around 230 mv then going to 0 when the Dashhawk would backlight that particular 02 sensor. The front 02 sensors do it more than the back. Under deceleration, all 02 sensors go to 0 millivolts.
Also, it seems like my rpm's are up 100-120 in cruise.

[BlueJacket]

Could it be that you are now getting a winter blend gas and that is what caused the change?

[GRRRR8]

Did you drop your air pressures from that snow you got caught in? Winter blend fuels will be a slight drop too.

[-Ray-]

According to state laws, ethanol blend gas should have a sticker on the pump. I have looked and see no stickers. Remember, I get gas in IL, IN, OH, MI when I'm in my car.
What about the o2 sensor millivolt issue?
Tires were at 37 lbs after they warmed up.
It also was in the high 60's.

[GTPprix]

My guess is winter gas and the colder temps

[Chewy]

Heck I'm averaging 15 or so! :wtf:

Of course I AM having a bit of fun with it and it's still breaking in a bit.

The trans gets better and better with mileage IMO.

Chris

[-Ray-]

My guess is winter gas and the colder temps

It was 70 in Plymouth this morning Chris. Stayed around 70 all the way home. I put Shell 93 in it at 5 Mile and Beck.
I ended up with 25 mpg. Easily off my Interstate avg of 27.3.
Company pays me when I drive my car. I write every tank and mileage down.

[Chewy]

It was 70 in Plymouth this morning Chris. Stayed around 70 all the way home. I put Shell 93 in it at 5 Mile and Beck.
I ended up with 25 mpg. Easily off my Interstate avg of 27.3.
Company pays me when I drive my car. I write every tank and mileage down.


I want 77.3!

[GTPprix]

It was 70 in Plymouth this morning Chris. Stayed around 70 all the way home. I put Shell 93 in it at 5 Mile and Beck.
I ended up with 25 mpg. Easily off my Interstate avg of 27.3.
Company pays me when I drive my car. I write every tank and mileage down.

Not sure about down that far but up here we are on winter gas, it sucks.

[Mike@NewEra]

The reason why your o2 millivolts go to zero when you are decelerating is because there is a function in the computer called DFCO , Decelleration Fuel Cut Off , which cuts back on the fuel during decel for multiple reasons .

The thing that catches my eye here with what you are saying is that you say your rpms are up 100-120 rpms at cruising speeds , which could indicate your convertor NOT locking up , now there are a few things that could be causing this if it is the case , but this will effect your gas mileage . Send a log to VMS since they are the tuner and they will be able to see if this is actually the case . Just my 2 cents .

[locrzn#92]

Mike, you are the cats meow.

[-Ray-]

Thanks Mike.

[GRRRR8]

Thanks Mike! Nice to see you here. I told Ray that when he called me as it is about the only thing I could think of that would cause both of his issues.