Terrible Mileage
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New User
Joined: Sep 2008
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From: Georgia
Terrible Mileage
87 f150, 5.0 EFi, 3.08 gears,and a 3 speed transmission. Trying everything to get better mileage. I got the K&N FIPK, Crane cams coil, Accel plugs,wire,cap,rotor, Shorty headers with the 02 sensor in the header, True dual exhaust ( no cats) With glasspacks,synthetic motor oil. Im burning almost a quarter of a tank in 17 miles with windows up and a/c off cruise set at 55. could it be not enough backpressure with that non restrictive exhaust Whats some products that may help or something i need to replace or try? Thanks
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
NO. First thing you got to do is stop trying to use the fuel gauge for milage calculations, these things are notoriously inaccurate. Reset your trip meter and record the milage driven and fuel required at the next refill.. that's your fuel milage. If it's still terrible then check fuel pressure, if the truck has dual tanks check for the fuel transfer problem, and also pull the codes to see if there are any EFI system problems. Fix any issues you find with these three items and you should be back to respectable milage.
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New User
Joined: Sep 2008
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From: Georgia
I ran a scanner to is at school. Showed 3 codes code 12- rpm out of spec (extended idle)....code 33 Evp not closing properly,i fixed this code.. and code 44 air management system inoperative. I think this code was thrown cause when i did my exhaust system there was a pipe going into my cats that i had to take off so it just leads to nothing. I only use my front tank cause my rear tank has a vent problem and has a strong gas odor. How do i go about checking my fuel pressure?
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
To check your fuel pressure, you need a fuel pressure gauge. That gauge gets attached to the Schrader valve on the fuel injector rail on the driver's side of the top of the engine.
Something else to check is the fuel pressure regulator--it's on the fuel lines near the firewall and you can do a quick check by pulling the vacuum line to it. If there's fuel in the vacuum line, replace the FPR.
Jason
Something else to check is the fuel pressure regulator--it's on the fuel lines near the firewall and you can do a quick check by pulling the vacuum line to it. If there's fuel in the vacuum line, replace the FPR.
Jason
Der Postmeister
Joined: Sep 2006
Posts: 6,859
Likes: 560
From: Long Beach, Calimexiforia
You could clean your combustion chambers w/ Seafoam.
YouTube - The Official "How To Use Sea Foam" from Sea Foam and GUY.
Bump your base timing a little. Maybe to 12 BTDC only, as you're already lean w/ that K&N setup on a non-MAF engine. Run stock Copper Core plugs if you do. You should be running them anyway w/ that K&N setup.
A 48K Coil (Less than .45 ohm) would allow you to run a .054 gap. Once again, Copper Cores.
You'll see a performance increase as well as better MPG.
Why don't you run that tube to the Cat?
YouTube - The Official "How To Use Sea Foam" from Sea Foam and GUY.
Bump your base timing a little. Maybe to 12 BTDC only, as you're already lean w/ that K&N setup on a non-MAF engine. Run stock Copper Core plugs if you do. You should be running them anyway w/ that K&N setup.
A 48K Coil (Less than .45 ohm) would allow you to run a .054 gap. Once again, Copper Cores.
You'll see a performance increase as well as better MPG.
Why don't you run that tube to the Cat?
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