Engine 11 Mpg?

Discussion in 'Fox 5.0 Mustang Tech' started by Landon116, Aug 13, 2014.


  1. Landon116

    Landon116 Member

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    Hey guys so I've actually been able to get driving around in my fox after all the work I've been doing on it. But I put a full tank in at the pump it read 12.6 gallons went in. I am almost out and have reached about 135 miles. That would be around 11 mpg. Now I'm going off of the gauge to judge empty. Maybe the gauge or odometer is wrong? The car has :
    Fresh 302
    GT40 upper and lower intake
    Cold air intake
    70 mm maf from thunderbird
    BBK 70 mm throttle body.
    3.73 gears
    04 bullitt size wheels
    Full exhaust
    Direct bolted fan
    And an aluminum radiator
    It has all emissions removed
    The car doesn't get very hot due to the direct fan which I think could be the culprit ? It is around the "A" on the "NORMAL" gauge which isnt in the middle. Im thinking it may be the fan or I need to tune for the Maf. No codes besides emissions codes. Maybe it's a fuel issue ? What should I look for ? The car is a 1992 hatch by the way. Thanks guys !
     
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  2. stykthyn

    stykthyn Commander of the snuggie cultists

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    What kind of driving are you primarily doing and what thermostat are you running? Auto or manual?
     
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  3. Landon116

    Landon116 Member

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    I have been daily driving for the last week for the first time since buying it. I basically granny shift and never above 2k rpm. I drive to school and back which is like 20 Miles round trip. I have gotten on it once or twice the whole time I had this recent tank of gas. I am running a Fail-safe 192 degree thermostat. It could be running rich? No codes though. Also I have NO power at WOT when cruising in say 4th gear going 45 at 2500 rpm. It will SLOWLY creep up in rpms. I have never driven a foxbody or a V8 before for that matter so I don't know exactly what it should feel like but it's not good lol. I'm still in high school and don't have much help from anyone so anything is appreciated!
     
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  4. stykthyn

    stykthyn Commander of the snuggie cultists

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    What tranny?
     
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  5. stykthyn

    stykthyn Commander of the snuggie cultists

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    Anywhoo at 45 you should be turning way less than 2500 in 4th gear
     
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  6. f8tlfiveo

    f8tlfiveo My wife likes my spool and blow-off valve.

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    I beat my car and get 18 mpg.. Something is not right
     
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  7. Landon116

    Landon116 Member

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    It's a t5 tranny , I maybe slightly off maybe more like 2,000 I'll check.
     
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  8. mikestang63

    mikestang63 Mustang Master

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    pull a plug and see if it is running rich. It could be a lot of things

    vacuum leak
    bad FPR
    incorrect timing
    bad O2 sensors
    bad cats
    crossover tubes clogged
    valvetrain not set up properly

    You mentioned you have a 70mm MAF from a T bird? what is the part number and what size injectors are you running
     
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  9. Landon116

    Landon116 Member

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    Okay got any ideas on where to start with an fpr? I will pull a plug and try to post a pic. You say proper valvetrain setup? Please explain more on what or why that could be. Yes the p.o installed a 70 mm thunderbird stock ford maf. I have 19# injectors. Also had a WOT relay wired in for a nos setup long time before I had the car, all was removed and fixed up but could any wiring mishap cause issues ? I'm I did a full tune up btw with ignition
     
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  10. stykthyn

    stykthyn Commander of the snuggie cultists

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    That maf is incorrect. Install stock or 94-5 gt maf
     
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  11. Landon116

    Landon116 Member

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    I have the stock Maf in the barn I can throw on and see if it helps? Can the 70mm maf cause issues ? I think he did it so it didn't bottleneck but I know the pcm uses readings from the Maf to send fuel to the injectors. I'm eager to learn so let me know what you think !
     
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  12. Landon116

    Landon116 Member

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    Okay if you saw my post I said I have the stock one that came woth the car. It looks like someone hacked it up though trying to port it. Not too bad But still intact... I'll go try that !
     
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  13. stykthyn

    stykthyn Commander of the snuggie cultists

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    Ugh. If someone tried to port it leave it alone. Find another unit. The maf is crucial abd any discrepancies Will cause poor running conditions. Almost sounds like your ecu is running in limp mode.
     
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  14. Landon116

    Landon116 Member

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    Well I put it on and youre right it is definitely running bad. The car runs pretty good in the lower gears it'll spin the tires no problem with the 70 mm maf but it just doesn't seem right. How can I tell if it's in limp mode ?
     
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  15. Landon116

    Landon116 Member

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    Just wondering but in a perfect condition, would a stock 1992 5.0 MAF work with a 70mm BBK throttle body? I would like to start over from what the P.O has done..
     
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  16. mikestang63

    mikestang63 Mustang Master

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    The MAF has nothing to do with the throttle body. For the purposes of this conversation and to keep it simple, a factory Ford MAF needs to match the EEC, and the MAF needs to match the size of the injectors . Aftermarket MAF's like PRO M can work with the stock EEC by "fooling" the EEC by adjusting the voltage sent to to the EEC.

    The T Bird MAF does not have the same signal or parameters as the Mustang MAF and will cause all sorts of problems. Put a stock Mustang MAF one on or one from a 94-95 Mustang GT and see if that clears it up.
     
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  17. Landon116

    Landon116 Member

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    Okay cool, I was always weary about that T bird MAF.. I guess that could explain the bad mileage and power issues? We will see, I bet changing out my oxygen sensors after 132,000+ miles wouldn't hurt either. Where is the best place to get a 94-95 MAF? Its my understanding there is an adapter for the conversion? Truly appreciate the knowledgeable information.
     
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  18. mikestang63

    mikestang63 Mustang Master

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    Best place to buy one is either check the message boards or junkyards. You can either buy or fab up an adapter. By now way am I trying to whore this thread out but I I just took off a 95gt 70mm MAF off my car as I swapped to a bigger one. PM me if you are interested.
     
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  19. Landon116

    Landon116 Member

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    PM sent
     
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  20. stykthyn

    stykthyn Commander of the snuggie cultists

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    Mike you whore
     
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