Fuel Economy!

Discussion in 'SN95 V6 Mustang Tech' started by XJay, Dec 11, 2006.


  1. XJay

    XJay New Member

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    My fuel economy on my '99 has progressively gotten worse over the last two years, and I've seen a change (for the worse) in the last three weeks. Next weekend, I'm changing the air filter along with Seafoaming the upper end of the engine - would it be helpful to run some through the gas tank/fuel system as well? I'll also be changing the fuel filter, plugs, and wires come February.

    My questions are simply, what could be killing my fuel economy, and what else can I do to improve it?

    Also, my engine stumbles a bit between 1100 and 1400 RPM, could this play into the problem with the fuel?

    One more -will a coldair induction kit improve or worsen fuel economy?

    Thanks in advance...
    #1
  2. Adverse2Change

    Adverse2Change New Member

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    You're taking the proper steps to improve it. A drop in K&N will help a small bit with MPG, as will a CAI. Are you also keeping up with your tire inflation and wear?
    #2
  3. 02ponypackage

    02ponypackage New Member

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    Check tires, maybe a better intake CAI with K&N or any good filter, fuel filter change, along with ne other needed filter changes
    #3
  4. XJay

    XJay New Member

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    I've changed the air filter, fuel filter, and plugs/wires. I've Sea-Foamed the fuel system (via the gas tank) and the cylinders (via the intake vacuum hose). Tires are correct size and inflation.

    Still, fuel economy is getting *ridiculously* worse. What else is there to do?????
    #4
  5. ChingonStang

    ChingonStang Member

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    It's probably the gas. This ethanol mix is crap.
    #5
  6. 232Mustang95

    232Mustang95 New Member

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    :stupid:
    #6
  7. ChingonStang

    ChingonStang Member

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    [​IMG]
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  8. V6muscle00

    V6muscle00 New Member

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    im with chingon.. the ethanol mix sucks
    but more importantly we def need more wookie and maybe some cowbell too
    #8
  9. raz54

    raz54 New Member

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    You can never have too much cowbell......


    Have you had the cats checked to see if any are plugged?
    #9
  10. XJay

    XJay New Member

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    I read in another fuel economy thread where someone suggested making sure that the Overdrive is still on.

    What is 'Overdrive', and how does it affect fuel economy? I'm assuming that since the light on the dash comes on when it's off, that Overdrive is meant to usually be on?

    I know where the overdrive button on my automatic stick shift is, but when I press it, nothing happens (no light on the dash) - what does this mean, and could it be affecting my fuel economy?
    #10
  11. XJay

    XJay New Member

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  12. 232Mustang95

    232Mustang95 New Member

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    The bulb might be busted and yes that will hurt your milage if it's off.
    #12
  13. ChingonStang

    ChingonStang Member

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    :stick:
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  14. Give Me TP

    Give Me TP New Member

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    OD is on by default every time you start the car, so it is unlikely that OD being off is the source of the problem. To comfirm though, find out what the rpm is at a given speed and compare that to what others on here experience with similarly equipped 99 models.

    Also +2 on need more kowbell
    #14
  15. TheCrazy1

    TheCrazy1 New Member

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    The rpm should be around 2200 or so at 70mph. At least somewhere in the low 2000 range. If it's way higher, then overdrive has left the vehicle! Sounds like you've done everything there is to do as far as basics to improve the mileage. What exactly is it getting per gallon? My g/f has a 2001v6 with manual trans and she averages about 23 to 24mpg. On a road trip, it'll do around 30! You say it stumbles a bit too... it might be worth your while to replace the coil pack... they seem to go out and cause misfiring, stumbling, etc.... How many miles are on your car?
    #15
  16. XJay

    XJay New Member

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    I've around 135,000 miles on my car. I'm wondering if I need to replace the fuel injectors......am I getting ethanol at the pump now?
    #16
  17. AP1995V6

    AP1995V6 Member

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    I usually get around 300 miles before I fill up - in the neighborhood of 1/4 tank.

    Is your CEL on? Running rich will definitely cause your gas mileage to crap out. Driving habits affect mileage alot. I dogged my car one tank and got around 18mpg. "Normal" driving got me around 22. And Casual driving got me 24. Most of my driving is on interstate or city driving so I never see anything over 25.

    Another thing you could do is to pop out the spark plugs and check their appearance. Make sure they're gapped correctly and such. Check brake pads for wear. A siezed brake caliper will make your gas mileage drop as well. Check the emergency brake to make sure it isn't sticking.
    #17
  18. XJay

    XJay New Member

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    Forgive me, what is a CEL?
    #18
  19. 232Mustang95

    232Mustang95 New Member

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    CEL = Check Engine Light
    #19
  20. jefferz

    jefferz Member

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    I think on the 99-04s they will say Service Engine Soon instead of Check Engine...just so you know. I just cant remember off the top of my head cause mines never been on in my 02 GT
    #20

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