Mileage Still Bad

[Tractor Dan]

Ok. I"m beginning to think this truck is just possesed and has a mind of it's own. lol. Ever since i got it September of 2008 it has had horrible mileage. Here is a list of everything that has been done.

Keep in mind this truck isn't exactly stock. It's got a 2 inch suspension lift all the way around and it's on 31X10.5 all terrians.

Spark Plugs-3 sets(Finally put motor craft in the 3rd go round and it fixed the rough idle.)
Plug wires
Ignition coil
Serpentine Belt
Alternator
Belt Tensioner
Radiator
Upper Radiator Hose
PCV Valve
Cleaned the MAF Sensor
High performance air filter
Vacume line repair

Within the last 2 weeks I have replaced the fuel filter(that was an ohh so fun adventure, thank the good lord for friends with vehicle lifts and tools out the ears. lol.) I also cut my exhaust off as close to the CAT as i could. The CAT is still in tact and functional, there is about a 8 inch piece coming off the CAT that i bolted the Cherrybomb Glasspack to.

So with all this being done the check engine light no longer comes on. However i still only get like 13ish mpg. The best i got was right after putting the Cherrybomb on and that was 15 almost 16mpg. So what i'm trying to figure out is what am i missing or not looking for? The old fuel filter was shot, i think it might have been the origional from Ford. The truck just hit 130,000 miles. I'm wondering if maybe it's something to do with my computer? I have read about reprogramming but not sure that would even help. I also change the oil farily regularaly normally every 3 to 4,000 miles. I try to stay closer to 3.

Any help though is appreciated. I know this thing is capable of getting decent mileage as i have read around the net of people with similar setups getting atleast 16 to 18. I'm not looking for a giant leap in numbers just something better then what i'm getting.

Thanks in advance for any help or insight yall can give.

Dan

 

[stmitch]

I'd suggest checking your o2's, and cleaning the air filter, injectors, and MAF for starters.

 

[chubster2003]

Cleaned the MAF Sensor
High performance air filter

I'd suggest checking your o2's, and cleaning the air filter, injectors, and MAF for starters.

you obviously didnt read the post very closely bud...



besides the point, i have a 99 ffv, 265/75/16 (31.6" tire), 4.10 gears (stock), and a 5speed. i get about 16-18mpg myself. how are you driving the truck? do you have an auto or 5speed? if its a 5speed, where are you shifting? if its an auto watch where its shifting, maybe get a programmer to fix shift points.

i shift about 4k, and try to keep it between 2800-3500 rpm when crusing. sooo... idk

i have replaced plugs (autolite double plats), new accel coil, and new wires. have changed ALL fluids (diffs, trans, t-case), fuel filter, air filter, the whole 9 yards. i have 123k+ and runs and drives like a dream. only thing i had do to was put a clutch in it about 120k, when my pilot bearing went, and my clutch was just wearing out.

hope this helps

 

[Tractor Dan]

It's an automatic. I would take a stick over auto any day. lol. As for when the auto shifts it peaks around 3,000 rpms a hair over or under. Where would i go to get the shift points reprogrammed? I'm going to google information on it just thought i would ask though?

Dan

 

[Big Jim M]

Well Dan you seem to have the milage problem that causes most milage problems.. Do you even KNOW what diff gears you have? I'd bet on 3:07..
Chub just told you he gets Ok milage with 4:11 gears and a 31.6 tire. Most bad fuel milage can be traced to too tall of a tire and the stock high gearing. Put some 26 inch tires on there and get your engine performance back..Or go get a 4:11 rear end and keep the tall tires.
Big JIm

 

[Rearanger]

My acceleration is fine with 16" wheels and 3:73 gears, never had a problem getting up to speed on hwy ramp.

 

[ForOffRoadDriving]

mine was around 14-15 with 30x9.50 bfg mts and 3.73 gears, when i stepped down to 217/75/15 (27.7x 8.50, my winter tires) i started getting 16-17mpg. i think the gears are the thing holding your truck back, especailly with it being an auto it just isnt getting into its happy spot for those gears when its shifting at or below 3000r's.

 

[Ranger44]

The exact reason why 4.10's are going back on my truck, I would like to go 4.56, but I have the 4.10's laying here.

The gearing, and the fact that the auto shifts incorrectly for the 3L. Get a programmer to change the shift points.

 

[Tractor Dan]

Ok. Went out and looked at my rear end i can't make out any numbers on it or find any. I'm sure they are there but with it being an Ohio truck they are probably covered by rust. Is there any other way i can tell what gears i have?

Also what are people's take on programming devices that tap into the computer?

Switching to different tires isn't an option because we are still paying off the 31's i put on back in September. Only thing i could do is drop back down to the stock ones i took off the truck. I do have adjustable camber bushings so i know it could be aligned fine and i have the lifetime alignment from the shop so no matter what route i go tire wise i'm covered on alignment.

Dan

 

[Big Jim M]

Dan do this: Jack up a wheel..put the tranny in neutral...mark the driveshaft and the tire..now turn the tire zackly one turn while counting the turns the driveshaft makes.. That will be your answer. the driveshft will turn either 3.1, 3. 25, 3.5, 3.75, or 4.1 turns. It really east to do. I mark the tire where it is neatest the ground and I mark the driveshaft where it is easiest to see the mark at 3.1 turns.. then I give it a twist or two to make sure of what I'm seeing. It is an exact measurement..
Big Jim

 

[stmitch]

Sorry I missed the part about cleaning the MAF! Gearing for your tire size can definitley make a big difference in mileage as well as performance.

Just for comparison's sake, my truck is a 00' FFV auto. My gears are 3.73's, and my tires are about 25" tall. I have an intake, cat-back exhaust, underdrive pullies, and an electric fan. I run my truck mostly on e-85 so my mileage is probably 2-4mpg lower than if I were using gasoline. With mixed driving conditions, I average 16-18mpg. On all highway trips with gasoline, I can get 26mpg. Despite what many will say,3.0's are actually capable of getting decent mileage from time to time!

 

[triumphrider-1]

Check your door tags for axle code and match it on this page:
http://www.therangerstation.com/tech_library/Axles.html

 

[Tractor Dan]

Well the gearing mystery is solved. It's a code 86 which is an open 7.5 with 3.73 gears. So after running it through the calculator i could possibly stand to go up to a 4.10. However my dad has already started shooting the axle swap idea down, i would pay for it all he just doesn't like the idea. Honestly i would think after putting lift blocks on my truck the rear end drops rather easy it seems like the pain in the neck would be unhooking everything. Am i correct in thinking this? I mean i know there is probably atleast a good 3 to 400 dollars involved in the swap but it would be worth it if it picks my mileage up. Maybe i should hop over to the axles section and do some researching. I mean if i get a 7.5 with 4.10 shouldn't it basically mount right up with little to no fab? Thanks for the advice and all the help so far. I went from being to atleast somewhat having a clue what i'm working with.

Dan

 

[basketranger]

just change out the gears, leave the axle in place. then the only tough thing is setting gear lash.

 

[vw505]

I put an FX4 rear in my B3000 it took about 3 houres and i bought it off craigs list. Look around you can find them and the 8.8 would be a nice up grade from the 7.5. I also am getting a little better gas milage, I have 235-75-15's on my truck so thay abe about 29" tall.