when I had my truck at the dealer for the trans I also complained about low mpg it was at 12 checking with a calc and the comp were close now its showing 9.6 on the overhead. The dealer said they didnt have a diesel mechanic then they said they hooked up there computer and it showed no codes. The truck seems ok once up to speed the eco shows 16-26 mpg but ontake off (15-1800 )rpm the eco shows 1-3 mpg until it gets up to speed is this normal? seems like take off is killing the mpg no matter how slow I accelerate. I checked the Iat sensor it was clean and reset the apps and no improvement

 

Wow thats pretty bad. I have a new one and don't reset my computer until I am on the freeway at speed. It gives me up to 26 mpg and the gets back to 17.9 to 20.9 ave. My goal is 20 mpg in my driving style. I have a 2wd also. Check the air in your tires. Mine fromthe factory was 35 psi. I raisied them to 60 and they are "E" so they will hold up to 80 psi which is what I will do in the summer. Goodluck.

 

Tires are at 55 psi If I floor the truck from a stop it will hesitate for a second or two before it moves unless im turning then the tires will spin ,The tank im on now the truck has not been over 2000 rpm and this is the worse mpg I have seen.

 

Mine always drops to 5-9 MPG when I'm using the "instant" mode during acceleration, even babying the darn thing. Then as I reach cruising speed, it levels off at about 19-24 mpg. But in the winter, I still only avg about 16mpg.

 

Have you checked your MAP and IAT sensors yet. They can be the root of bad mileage.

 

If I'm understanding you right you are seeing low MPG numbers while your trany is shifting up to high gear while in instant mode (what the mileage is that second). That would be correct, in the lower gears (1 to 3 mpg) you do not get as good fuel mileage as when in overdrive (16 to 20 mpg). It sounds like you are reading instantaneous fuel mileage and not average mileage.
Hope this helps.

 

the avg is 9.6 ive had the truck for 2 months my first tank on paper was 14 second tank was 12 and the comp was close now its reading 9.6 and the fuel guage is dropping a lot faster

 

Sounds normal to me.

Hesitation is from Torque Management.

I was actually thinking,, "Wow, you are getting 5MPG on accelleration."

Much better than my Mothers '98 Lincoln Navigator that was on Zero anytime the truck was trying to keep up with traffic.

BTW, Keep the RPM up, try to operate in the 1,500 - 2,200 range, and your Mileage should go up.

Keeping these motors at low RPM is not good.

The Big Cummins spin low RPM (big rigs), but this (our trucks) is a baby motor, and it will easily, and efficiently spin medium, to high RPM.

Tell us what you find out with average driving, keeping the RPM up a little more.

Merrick

 

ill try to accelerate a little faster but my f150 was getting better mileage guess I should have kept it

 

Weak lift pump, dirty fuel and air filter, MAP and IAT sensor, and winter fuel can all attribute to poor mileage.

You stated that you pulled and cleaned the IAT, but it may still be bad. I can not for the life of me remember the voltage levels for a properly functioning IAT at certain given temps. The same goes for the MAP sensor. IF it showing a high boost than actual, it will be dumping more fuel than needed.

Is your truck stock? Power mods (injectors, fueling/timing box)?

How about bumpers, grill guards, camper shells (toppers)? Our trucks are about as aero dynamic as a brick, and anything we bolt on to the outside usually makes it worse.

Are your brakes dragging? Alignment OK?

Where are you getting your fuel? Busy station, moves a lot of diesel?

Lots of things that are simple can kill ya. I was getting consistently 16-17mpg in the city 19-20 highway, then after my first LP replacement, I dropped into the 14's city and high 16's highway, and this was over a 5 month period. I also acquired a topper, and a grill guard at the same time. Topper is gone, LP was relocated to the frame rail by the fuel tank, and the Edge EZ is off most of the time. I just got back into the 16's in the city over the last two tanks and the highway looks to be back to normal as well.

 

havnt changed the fuel filter dealer should have with maint agreement but all they did was change oil, when I first turn key on I hear a squeeky sounds like a rusty bed spring sound for a second is that the lift pump? truck is stock as far as I know. filter looks a little dirty but the little meter thing is showing it as good.

 

tried keeping rpms around 2000 =9.4 mpg avg on overhead

 

I'd have a look at the fuel filter.
Most around here change them at 10 -15K, who knows when it was changed last.
Don't get the filter from the dealer, much much cheaper directly from Cummins or online.
If you haven't changed it yourself, you really have no idea when it was changed last.
If it is still the original ,ouch.
If it were me, I'd change it regardless, then you know for sure.
12 bucks and 15 minutes of your time is worth hit.

Don't trust the little air filter minder thingy.
I got rid of my stock filter and airbox at 20K and it was disgusting.
Oily gunk, tons of dirt, bits of leaves and decaying small animals but the filter minder hadn't moved a millimeter.

Also, don't trust the overhead, it isn't accurate that often.

Mine shows an average of 11mpg, but hand figuring I'm getting 13-14 on winter fuel, which IMHO isn't bad at all, the way I drive.


phox

 

I am going to napa to get a fuel filter today. the air filter has a lot of bugs and crap in it so I will probably replace that to. Guess ill search to see how to replace the fuel filter. If I get a bhaf will I have any warranty problems?

 

I put a NAPA filter in mine the last time I changed it, mainly because I had been a nice guy and lent my spare to someone else and forgot to replace it. I was out on the road and had no choice.
I did notice a couple things about the NAPA filter though. It has bigger openings for the fuel to flow through once it gets through the paper. The element paper size was a tad smaller but I personally believe it will flow better. Just my opinion.