99 B-3000 Mpg 12-14

[pawpaw]

Are you using E-85 in your flex fuel engine????

If so, then expect lower mpg.
If not, also consider putting the flex fuel sensor on your suspect list for check out.

I'd also check the O2 sensors switching speed. A whiff of coolant won't do them any good.
Also with 90K on them, they might be lazy, so check their switching speed out with a scantool.

Sounds like you have/had several issues, all of which would likely affect driveability.

Let us know how it goes.

[tomw]

You may have kilt your O2 sensors with anti-freeze if it got into the exhaust when the H2O got into the oil. That would lead to the 0174 code. Remember: Low==Lean. When the O2 sensor starts to fail, it will stop producing the .9x-1.0v signal indicating no extra O2 molecules in the exhaust. It will produce lower voltages, such as when there are extra O2s in the exhaust(lean mix means not enough fuel to use up the O2s). That can give a 'lean' reading, and also cause the ECM to kick up the fuel it is sending because it thinks the engine is running lean.
If it runs bad cold, check the ACT and ECT sensors. I guess you did not replace the thermostat. How long does it take for the coolant to reach normal temp? It should take less than a mile of driving before you should see the gauge moving. If longer, you might want to consider a new thermostat.
tom

[chief31956]

not using E-85 its not here yet, flex fuel sensor i dont even know where the ff sensor is.
Alot of good ideas here to check out thank you, there is another thing i wound like to clear up due to the terminology i used, its not a scan toll its the INNOVA 3100 code reader so i am limited to what i can do, i would love to have a tool so i can do these test with, but i have no idea which is a good one, thermostat is cheap and easy to replace i ve had it 3 yrs now. FYI since i regapped the plugs MPG came up to 14.46 from 12.33

[duckshepherd]

Wait, did someone say a clogged EGR can hurt gas mileage and performance?

[chief356]

What's the norm for mpg on the 3.0 auto going to the junk yard thursday to get a bunch of parts so i can pinpoint this problem