Poor gas mileage
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Senior User
Joined: Dec 2015
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From: Longview WA
Poor gas mileage
So i have a 93 f150 5spd 5.0. Just put a new engine in the truck which runs great, But im getting really bad gas mileage.. 10mpg highway 13mpg in town. Ive done spark plugs, wires, cap, rotor, fuel filter, air filter, timing, TPS, IAC, checked tires for air pressure, Tried non ethanal. Nothing seems to help and it runs a little rich from what i smell.. So suggestions? only code is 11 and CM 33. Im scratching my head wondering if injectors could be to blame but i dont see gas on any spark plugs they are all a hazy white color.
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Senior User
Joined: Dec 2015
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From: Longview WA
5spd transmission not sure of the model rear axle is 3.55 with tru trak i think is what ford calls it, 31x10.5R15 tires at 35psi, Single rear tank swb and no have not checked fuel pressure im assuming its a gauge that goes to that schrader valve on the line?
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Yes a gauge will fit on the shrader valve on the fuel rail. You should see 32-35psi at idle and 39-45psi with vacuum removed, and the system should hold pressure after the engine is shut off. If it doesn't that suggests a leaking injector.
How exactly are you calculating fuel consumption? The fuel gauge cannot be used at all it's way too inaccurate, best way is over several tanks of gas recording the gallons/liters used and miles/kilometers driven.
Other things to check, the vacuum line attached to the regulator for presence of raw fuel.. suggests a leaking regulator, and the vapor(charcoal) canister for the presence of raw fuel though its not likely you will see any here as this is a single tank truck.
How exactly are you calculating fuel consumption? The fuel gauge cannot be used at all it's way too inaccurate, best way is over several tanks of gas recording the gallons/liters used and miles/kilometers driven.
Other things to check, the vacuum line attached to the regulator for presence of raw fuel.. suggests a leaking regulator, and the vapor(charcoal) canister for the presence of raw fuel though its not likely you will see any here as this is a single tank truck.
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Senior User
Joined: Dec 2015
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From: Longview WA
I calculate by average miles per fuel consumption of a gal over 3 tanks, and alright guess i need a fuel gauge to go find out if i got a leaking injector.. all the spark plugs are dry but that probably doesnt mean anything huh?
Logistics Pro
Joined: Aug 2010
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From: Chillicothe
Basically the same truck I have, and I get 15 to 17 depending on how I drive. Is it a new engine from a truck, or is it just a "remanufactured" engine? Of its a reman it could be like the 351 I picked up for my truck that was a generic "reman" that didn't have a fuel injection friendly cam so it got crap mileage.
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Senior User
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From: Longview WA
Its a New remanufactured engine i made sure it was the correct one.. i got the same mileage in the old engine also..
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Joined: May 2014
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From: san jose
Old cats? Sticky brakes? Bad alignement. All of these affect gas milage. Old plug cats would be a big one
Also conanski, what garage have you used on the shrader valve? A test gauge or one that's mounted permently?
Also conanski, what garage have you used on the shrader valve? A test gauge or one that's mounted permently?
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Thread Starter
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Senior User
Joined: Dec 2015
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From: Longview WA
timing is set at 12 BTDC and no clue on Rpms.. id guess 2.5k to 3.5k depending on hills and where im at.. no Tac in this truck yet. The exaust was done in 2014.. all new cat, magnaflow and 3" all the way.. Previous owner did this..
Logistics Pro
Joined: Aug 2010
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From: Chillicothe
I've noticed when I wind her out more before a shift, she drinks more fuel. Since you don't have a tach, just try shifting a little sooner than usual. If I remember tomorrow when I go to work I'll look at my speedo when I shift. Then hop on here to give you an idea of when to change gears and see if the mpg goes up. Also, what is the terrain like where you live? Hills, flat, combination?
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Senior User
Joined: Dec 2015
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From: Longview WA
Terrain is mostly hills until i hit the I5 corridor. I think ill go drop it off get front brakes looked at for warped rotors, get new coil springs and an alignment done. Thats one thing i havent done since i got this truck.. If thats not it than guess its time to fire up the tig and try my hand at exaust lol
Logistics Pro
Joined: Aug 2010
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From: Chillicothe
Well hilly terrain will hamper mileage, with the 31s if you are under 45ish on the hilly back roads just run in fourth to see what mileage does. And when you are on the i5 what's the speed limit? Over 60-65 my mpgs fall like a rock.