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Fuel Economy Problem (help me troubleshoot)

Discussion in 'Other Vehicle Discussions' started by Capt. Orygun, Jan 23, 2007.

  1. Capt. Orygun

    Capt. Orygun Win the Day

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    So when I bought the 97 S14 and sold the 99 SI one of the long term bennifet's I cited in my decision was that owning it wouldhelp me to learn more about working on cars. For those of you who don't know I was an aircraft mechanic for 6 years so mechanic repair isn't hard for me I just don't have allot of experience doing it with cars. Or rather I should say didn't lol.

    Since I bought it:

    Tie Rods
    Front Lower Ball Joints
    Front Cover Seal
    Alternator
    Waterpump

    I'm sure I left something out, but everytime the process is the same, I find someone who can tell me what's wrong, I buy the part, locate it under the hood, and change it no prob lol.

    Well here's he latest problem

    In the last 700 miles or so my fuel economy has sank from 22 all way way to 16MPG

    some useful info

    Spark plugs are plat and 2 years old
    Wires looked new when I bought the car two years ago
    vehicle runs smoothly
    I use 92 octane
    Fuel Filter is a year old
    There is obviously no leak, I'm not a dumb ass

    Any idea what's wrong?
     
  2. hcivic.com

    hcivic.com Senior Member

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    check you plugs and wires usally number 1 cause
     
  3. ScrapinSi

    ScrapinSi Senior Member

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    Main causes of poor gas mileage are as follows...

    #1 = Plugs & Wires
    #2 = Air Filter
    #3 = Fuel Filter
    #4 = TIRE PRESSURE (This kicks alot of people in the ass)
    #5. Depleted Oil Quality (Motor/Tranny/Diff)
     
  4. Celerity

    Celerity Well-Known Member

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  5. Celerity

    Celerity Well-Known Member

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    Actually, I take that back . ECU can do it too. The Neon will get 30 mpg one tank full, 19 the next. I have no idea why. Then it gets back up. Last tank I averaged 26 mpg and the one before that I made it to 32. This tank I'm going to take to a hair over 200 mpg which is less than 20 mpg. (My alternator shit the bed in the middle of Rural Connecticut late at night, had to hammer that shit home)
     
  6. Seany-izzle

    Seany-izzle New Member

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    do you warm up your car before you drive it?? i usually see 27-30 around town, but last winter when i used my car a lot more and warmed it up most of the time, it was down to below 20.

    im sure if you did that youd realize it, but hey.. who knows. :p
     
  7. E_SolSi

    E_SolSi Member of the 20 nut club Moderator VIP

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    cold weather makes the car run a richer AFR
    letting the car idle for 30 minutes warming it up every morning before work kills your MPG
    in the winter gas companies add more ethanol to the mix to "keep gas lines from freezing"... more ethanol makes the car run richer AFRs, it also burns less efficiently, it also creates less power forcing you to drive harder to try and get the same performance out of the car
    so ethanol = richer AFR = lower MPG , less eficient burn = lower MPG, less power = drive harder = lower MPG

    and just for shits and giggles while im on the subject... ethanol not only kills your MPG, its also a lot harsher on your entire fuel system (pump, lines, injectors, etc...), and it will reduce the lifespan of your engine significantly
    yay ethanol!!!
     
  8. Capt. Orygun

    Capt. Orygun Win the Day

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    Well my plugs are 2 years old and I'm pretty sure the wirse aren't much older but I could change them

    When I filled up yesterday I was a quart low on oil but.. nahhh

    air filter was recharged a month or so ago

    tire pressure is fine

    fuel filter is a year and a half old

    I do warm my car up every morning though, for about 15min or so

    I have a new PCV valve too, doubt it would help much cause the vehicle is running smoothily but I have it laying around so I guess I'll change that out too

    any other ideas?
     
  9. Celerity

    Celerity Well-Known Member

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    Warm ups will do it too.. although I have no idea why, really.
     
  10. Capt. Orygun

    Capt. Orygun Win the Day

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    but this is only during winter? I have owned this car for going on three years in March and I've never noticed this before
     
  11. Capt. Orygun

    Capt. Orygun Win the Day

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    Oh, and I started using COSTCO gas too
     
  12. totalburnout

    totalburnout Well-Known Member VIP

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    Depending on the setup, when its cold their could be fuel economy problems as well.

    I pull the tumbler generator valves from the WRX that help on cold start ups, the weather gets cold, and my gas mileage shoots into the shitter.

    Also, with forced induction you may be boosting that much more and that much harder now that the humidity has dropped and its so cold. Have you datalogged anything?

    If I were you, I'd start with plugs and wires/coil packs (I'm not familiar with the sr so I don't know what it runs). Tire pressure is another obvious thing. I'd personally check for boost leaks as well, just to make sure that you're not feeding the car a ton of gas, only to have power robbed from the car through a vacuum/boost leak.
     
  13. totalburnout

    totalburnout Well-Known Member VIP

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    Haven't you heard that brand of gas means virtually nothing? All gas is brought in by ship or pipeline by a few key players and divvied up between oil companies. Its the same shit, different day. Some places like Hess and Mobile add their detergents and additives but really there's no such thing as one retailer having "bad gas" on a regular basis.

    They actually say to go to the busiest gas station because the tanks will be filled the most often and then you won't have to worry about getting any sludge from the bottom of the tanks or any old gas.
     
  14. Capt. Orygun

    Capt. Orygun Win the Day

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    Holy cow dood it's a fucking stock KA
     
  15. totalburnout

    totalburnout Well-Known Member VIP

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    ...I thought you swapped a Sr into it last year.

    I thought both you and get_nick had sr20'd 240's.


    :ph34r:
     
  16. Capt. Orygun

    Capt. Orygun Win the Day

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    nope had a major career change, wanna buy a pickup at the end of 07, will gut the S14 and do it right
     
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