gas milege sucks

[ghost_rader]

I have a 94 4.0 ranger 5spd and i am sure somethhing is wrong, but i can't figure it out. i am getting around 10 mpg weather i am on the highway or driving around the city. I have given the truck a full tune-up plugs,wires,air, pcv, fuel filter, it has a new converter, new o2 sensors, cleaned the maf, the fuel pressure reg, and i drive very easy. my truck now has a 4" lift and 33" tires but it hasn't changed mpg since the lift(was this bad before that lift. the gears are stock(3.27) and i have an aftermarket exhaust. i have been looking around for a while to see if anything could help and can't seem to find anything that seems right. the truck seems to run very well(doesn't idle badly, or smell like raw fuel) any help would be much appreciated

 

[rags]

My thought would be the 33" tires! Your odometer is not reading your miles traveled correctly. Your speedometer is off also if you haven't replaced the gear on the cable.

I hope someone else will chime in and give the formula for figureing your milage with that size tire.

 

[Donnie strickland]

Yep -- 33" tires will throw off your speedometer quite a bit.

In addition, 3.27 gears are really too high to use with 33" tires. 4.10 or lower would be much better. The gearing/tire combo is part of what's lowering your mileage.

 

[joes4X4ranger]

Tires for sure, even a small size increase will drop gas mileage. I've got a 91 Explorer, when i changed from the stock 235's to 31X10.5 my gas mileage went from 22- 17. I running 3.73 gears and had a dealer fix me up with the right speedo gear. I've had 2 cops clock me a different speeds and my speedo is correct.

 

[ghost_rader]

i agree with the tires throwing off my speed, but the milege sucks with the stock tires as well

 

[MAKG]

Jeez, guys, can't you guys calculate?

If 33 inch tires cut the apparent mileage in HALF that would mean stock tires are 17.5 inches. No, they aren't. Tire size does NOT explain the mileage measurement.

As for P235 -> 31 inch tire mileage loss, no. I did the exact same thing. Corrected mileage was virtually identical. Perhaps driver error is responsible there (watch your tach). Gearing doesn't matter unless you drive around in 1st gear a lot.

There is a REAL problem with this truck, so stop saying that's just the way it is. No, it isn't. And it's going to take some very difficult diagnosis to figure out what the problem is. This is not something one can guess at.

 

[ghost_rader]

thanks makg, i am pretty mechanically inclined, but do not have alot of the diagnosos equipmant i need to figure this problem out the parts i have replaced were not chasing this problem and throwing parts at it just things that needed to be done anyone with an idea on where to start i would really appreciate it

thanks

 

[96xltV6]

get a volt meter, test the TPS current. Turn your key to the on position but dont start the truck. It should be at .96 dvc. if its more, thats whats happening. that would cause you to run rich.

 

[MAKG]

get a volt meter, test the TPS current. Turn your key to the on position but dont start the truck. It should be at .96 dvc. if its more, thats whats happening. that would cause you to run rich.

Care for any other random guesses?

And it's wrong. Incorrect TPS setting will be quickly and automatically adapted for by the PCM, at least until the air bypass maxes out (which would require a LARGE offset).

It's not possible to determine what's wrong with the vehicle only from a description of poor mileage. It needs to be diagnosed. If you can't figure it out, you need a professional.

I'd start with self tests, spark plug inspection, and a fuel pressure check.

 

[Donnie strickland]

MAKG -- of course you are correct, but notice what I posted earlier:


"The gearing/tire combo is part of what's lowering your mileage."


Notice I didn't say that was all of the problem.

He said in the original post that the mileage was bad before the tire swap. I agree there are deeper problems, but my point was the tire size will make it more difficult to calculate the actual fuel mileage when the problem is fixed.

As you have pointed out it's going to take some diagnostic work to pinpoint the problem; I just didn't want to engage in idle speculation.