4.75 Mpg....
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Fleet Mechanic
Joined: May 2004
Posts: 1,436
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From: Montana
4.75 Mpg....
Ok so what would cause my 92 f-150 to do such a thing?Its got a 5.8 with 37,000 miles on a rebuild. It runs real strong and doesnt have any problems accept the occasional idle surge that all EFI fords are notorius for. It has been getting worse over the years but never this bad...I went 9.5 miles and i used an 8th of a tank ifnot a little more! I can phisically watch the guage drop as i drive....and most of my driving is at 50-65 in overdrive. Now before anyone suggests it NO there is not a leake in the tank or anywhere else, I have been down that road. All i can figure is i need new injectors.
Elder User
Joined: Jan 2006
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if you have two tanks, do your measurement on a full tank until its near dry. when it does, switch over to the other tank, then find your mpg. I cant trust my tank gauge. When I fill it full, its well over the full mark, and it suddenly goes from half tank to 1/4 tank within a few miles. I ran my truck on "E" for 20 or so miles before it started missing.
Senior User
Joined: Sep 2006
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From: cleve,oh
mine front tank say below empty and back tank says its coming out of tank i gave up on it im just gonna disconnect back tank and try to fix front from what ive read the dual tanks in these trucks were designed by 4th graders in beverly hills in thier study hall
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Fleet Mechanic
Joined: May 2004
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From: Montana
I have duel tanks but I have done this with varried levels of fuel and it goes really quickly..not like a jump in the guage just a very steady decrease. Its 10 miles to work and 10 miles back and thats a 1/4 tank everytime no matter if its full, half or quarter tank...The guage always travels the same distance. I even thought about tank slosh but I waited and ruled that out too. It used to get 10 mpg but I dont know whats up now. Is there any parts that will ruin your fuel milage like that? I know if your injectors are bad it can happen but I cant fathom any other parts... I think I should atleast be getting 15 mpg out of this thing. I used to be able to drive over 60 miles and back and not used a half tank now I cant drive to the other side of town and back.
Senior User
Joined: Oct 2004
Posts: 371
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From: Wetaskiwin, Alberta
What is the general state of tune that the motor is in? What work have you done recently that should have actually helped fuel MPG, you know, plugs, wires, filters, that kinda stuff. Man, that is some kinda crappy gas mileage. My '91 with the 5.0 is delivering a steady 17mpg (US conversion, about 22mpg up here in Cda.). Even the 10mpg that you used to get is not very good, even for a truck with the 5.8. Any chance that the O2 sensor could be in need of a change out for a fresh one?
I dunno, I want to say start with the simple stuff but you've probably covered all the basics already. Does the color of the tailpipe(s) maybe indicate that it's running rich? What about the color of the plugs?
Just a few thoughts - wish I could be of better help to ya.
Cheers!
Mike
I dunno, I want to say start with the simple stuff but you've probably covered all the basics already. Does the color of the tailpipe(s) maybe indicate that it's running rich? What about the color of the plugs?
Just a few thoughts - wish I could be of better help to ya.
Cheers!
Mike
New User
Joined: Feb 2006
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mine done what your`s sounds like,, you know how the fuel gets bypassed and sent back to the tank? mine while using the front tank ,, it was sending the bypassed gas to the rear tank but drawing the gas from the front and making the guage go down steady and faster than it should
i forgot i ran out and switched to the back which was about empty too went to the station and filled up the front, switched back to front tank , got home just for giggles checked the back and it had went from empty to half a tank
flipped it back and forth a few times and it started working right
may not be whats wrong with yours but its a thought
i forgot i ran out and switched to the back which was about empty too went to the station and filled up the front, switched back to front tank , got home just for giggles checked the back and it had went from empty to half a tank
flipped it back and forth a few times and it started working right
may not be whats wrong with yours but its a thought
Post Fiend
Joined: Oct 2006
Posts: 7,269
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From: Where's my map???
The coolant temp sensor will do that. If its not reading op temp. It will dump more fuel to motor. I changed mine and almost doubled my fuel mileage. I also retimed and reset puter,by taking off neg. cable for twenty min. Hope this helps.
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Fleet Mechanic
Joined: May 2004
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From: Montana
Well the tune up is fresh, plugs, cap, rotor, oil and air filter. I know my new transmission will help but not that much. I had a friend who had bad o2 sensor on his dodge that caused the same condition but his check engine light was on...I ran a scan and it all came back good but I guess it can be dirty and still not pop a code. I never thought about the engine temp sensor, my water pump just got replaced but my radiator needs to be replaced now but it still runs cool and seems to be accurate but then again its the original cluster guage. A sending unit is cheap I might as well change it.
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Senior User
Joined: Oct 2004
Posts: 371
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From: Wetaskiwin, Alberta
OK but don't forget that there are two temperature senders on your truck. The 1 wire sender is just for your guage. The other temp sensor, the one that I think tewferford is referring to, is the one that feeds the engine temp stats to the EEC and this is the one that will screw up your MPGs.
Someone please jump in here if I am wrong on this!
Cheers!
Mike
Someone please jump in here if I am wrong on this!
Cheers!
Mike
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
what temp tstat did you install in the motor? also pull codes before you go replacing stuff. www.fordfuelinjection.com has instructions and will take 10mins at most
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Fleet Mechanic
Joined: May 2004
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From: Montana
well you see thats the thing I havent got any codes popping....my ecu is clean. I have code reader that is really nice...Ipaid about 150 bucks for it and it has helped with alot of engine light stuff. Are you saying that there could be codes and the code reader isnt going to detect them?
I didnt know there was another engine temp sensor other than the one that goes to the guage i thought it did both....where is the other one?
I didnt know there was another engine temp sensor other than the one that goes to the guage i thought it did both....where is the other one?
Last edited by EgoMan; Oct 19, 2006 at 03:12 PM.
Thread Starter
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Fleet Mechanic
Joined: May 2004
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From: Montana
ill run it again but it always comes back systems pass. It registered a code before that popped due to the IAC being unplugged...So i know it has registered codes before and I have fixed them both KOER and KOEO. Thats why I suspect something just being worn or dirty not failed. I mean if the O2 sensor was bad my check engine light would come on and my code reader would have detected it last time I scanned it which was only a few weeks ago. I think???
Senior User
Joined: Nov 2004
Posts: 336
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From: Pittsburgh!
Check under the truck for a big puddle of gasoline! 
No, really with mileage as bad as your's this should be an easy problem to find... severe stuff shows up faster. If you get it fixed I bet the truck will run much better too.
No, really with mileage as bad as your's this should be an easy problem to find... severe stuff shows up faster. If you get it fixed I bet the truck will run much better too.
Post Fiend
Joined: Oct 2006
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From: Where's my map???
Im telling you mine went bad with no warning and no codes. Its like a choke being half stuck and just pours more fuel in. I could actually watch my fuel guage move when i was driving. I don't know where it is on yours. The I6 has it right near the T stat housing. Hope this helps. It was around $25.00