I've got a 99 3.9 4x4 club cab. I've got 150lbs in the back for weight due to Ohio winters but I didn't expect the gas mileage to be this bad. I never had to engage the 4x4 on normal driving yet, only to get in and out of my driveway (snow+ long hill) the thing is I never get any better then 12-13mpg. I am light on the throttle, and have put some work into it so far but not much. What can I do to improve my gas mileage.

So far I have done plugs, wires, cap, and rotor.
Air Raid Air intake
195F stat stock replacement
Radiator Core flush

All my tires are at the proper PSI, and I check them weekly.

Any thoughts?

 

You could throw it on a dyno and see what your A/F ratio is, maybe its running to rich. (ie the computer over compensated for fuel when the mass air meter sensed more air from the Air Raid_

 

do ay warm it up in the mornings, dumb idea but it would affect the gas milage...my 2002 4.7 gets 13 combo driving, been told that the O2 sensors could be bad BUT its only a high of 6 here in iowa today so ill mess with it when it warms up Could be the same with urs...

 

I don't let it warm up much, maybe 3-4 min while I brush off snow. The thing about the Air Raid, I have not noticed any change after installing it, negative or postive. I am consistantly tank after tank 12-13mpg. Most times when it was warmer I was on the upper end of 13 like 13.8 14.2 but that was back in December.

 

by googling I found this... hmmm worth a shot

http://www.dodgedakotas.com/boards/v6/853-1.html

 

I have a good question for you. Where you are, is the temp at, or below 35-40 degrees? Whenever your IAT sensor detects temps at or below 35-40, it will automatically advance your timing. This will in turn stunt your gas milage.

 

Its 12 degrees outside right now.

I know that the IAT does this automatically, but like I stated before, even when it was 40-45 even 50 the best I ever got was upper 14's 15 in the beginning of December/ November.

This is whats throwing me off. I'm not throwing any CELs, theres no real way to check if my O2 is bad. I could just go out and get another sensor for the hell of it, but if it doesn't fix it... Then I'm out that money. I'm just trying to think of the next logical step to check, the o2 sensor route seems the way to go, I'm hunting for other ideas as well. If I do this and find some positive results I will definitely post them. I'm just trying to cover everything... I'll do the o2 sensor this weekend and report back for sure but I would like to check some other things as well.