I took my '97 F-150 4x4 into Ford for the tranny shutter. Was getting 14-15 mpg at the time. They did a flush and refill and it stopped the shutter. Since then I've been getting 10-12 mpg, and now that the cold is kicking I've gotten 8-9 mpg out of my last two tanks. I took it in and they told me that they did a mpg test and the computer said I was getting 15-16 city and 20-21 highway. They told me this as my truck was sitting there with 172 miles on the oddometer and the refuel light shinning on the dash. The computer shows no codes, nothing. My mechanic said to start by replacing the thermostat and O2 sensors( one of which was just replaced by Ford). Any thoughts???

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Red '97 F-150 SC 4x4 off-road, 16" rims instead of factory 17"'s(borrowed from old '97 reg cab), BFG 265/75 16 all terrain T/A, K&N filter with modified air box, Flowmaster 40 with duals out back, Expedition center console, 3" rear seat lift, after market stereo seen at HTTP://members.sounddomain.com/red97

 

I'm having the same problem with my 1996 F-150, the tranny shutter and bad gas mileage, i've got the truck in the shop right now getting the tranny flushed and filter & fluid replaced. this weekend i'm going to change the plugs, wires, rotor and cap and oxygen sensors to see if that helps out, i'm getting 10 to 13 mpg, and should be getting 15 to 18mpg from what everyone tells me.

 

the wds does show instant fuel economy so if that is the true reading than that is the milage that the vehicle was getting durring the test. Ford has a tsb on fuel ecomomy and the different factors that change this, one example is different terain, driving on pavement is much different rolling resistance then driving in sand, snow, etc. As for your transmission when was the shudder ( is it comming from the lockup convertor?, is if the convertor is not locking up that can reduce fuel economy a bit . And the amount of milage per tank is not an accurate way of determining milage, the accurate way is an acutal measurement of how much fuel is used, this is done on an average of atleast 3 tanks of fuel to be accurate. I had a customer return as i told him there was nothing wrong with his vehicle ( in this case i looked at it so i know there wasnt anything appearently wrong) he did however have an oil impregnated filter, i told him to put in the factory one durring the winter he wouldnt, then came back complaing about the fuel ecomny was worse than before he brought it in ( i never did anything the first time but check for codes and monitor pids and fuel trims, so impossible) i checked he still had the oil filter in it, i road tested it to begin with and recorded the milage, change to a ford filter (he said that he know engines and an oil empregnated filter isnt goint to do anythng compared to a factory one and he wasnt going to pay for it) well i put in the ford air filter and cleaned the maf and retested the fuel ecomy - an improvement of 2 mpg (imperial gallon), needless to say he paid for the ford air filter. The problem is in cold climates oil impregnated filters will frost up and limit air flow, how many oil air filters have u seen on sleds? Gennerally speaking if u are using an excessive amount of fuel the check engine light should come on in a period of time, check tire pressures and by the way accessoris also create fuel ecomeny loss, a bug deflector 1-2 mpg, running boards, etc they all add up, you could still have a problem but it depends on what tests were performed.

 

hey blackf150offroad.
Basically what i gatherd by what your saying is that a K&N air filter that is oiled for exapmle in cold weather "what tempratures may i ask its important" the oil will frost up restricting air flow? woa.. things definitly brings a whole new @#$@#4ing perspective to a K&N air filter if this is true i must say.
Well in my situation i live in southern california where the lowest the temp really ever drops is maybe 48F once in a while but usually 55F in the winter. Please shine some more detail on this.. GOD sometimes you think your making an improvement when it could be worse lol!

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F150 97 4.6 v8 longbed
K&N Air filter
Hyper White xenon bulbs
Bedliner and Shell
6 disc cd changer

 

I had my tranny flushed, new filter & fluid put in today and the shutter stopped (at least for now). Tonight i'm going to replace the cap & rotor (last week i changed the plugs & wires), the fuel filter, air filter, and also both O2 sensors to see if my gas mileage gets any better. right now i'm getting about 10 to 13mpg, i'll keep you posted to see if it gets any better.

 

Well, I think I have found the culprit. I changed my O2 sensor. So far I sitting at about 80 miles on a 1/4 tank of gas. Before(when it was bad) it would be sitting on about 45-50 miles on a 1/4 tank of gas. Hopefully this has fixed the problem. Ford had replaced one of the O2 sensors this summer so I just replaced the other. I'll keep you informed as to how good of gas milage I'm getting now.

 

Well, right now I'm sitting at a little under a half a tank with 163 miles on the odometer. I am very happy with that. That would sit me, at the present rate, getting about 283 miles on this tank which would be about 14 mpg all in city driving with winter time temps. I can defenately live with that. FAR CRY from getting 8.