'97 Hx gettin' 28MPG. Whats wrong?

Discussion in 'Engine Tech / Drivetrain' started by HeX, Oct 13, 2011.



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  1. HeX

    HeX Authoritah, respected. Staff Member Registered VIP 5+ Year Member

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    '97 Hx gettin' Low MPG. Whats wrong?

    Any suggestions on why my manual '97 Civic Hx is only gettin about 28mpg, or about 250 miles per tank?

    Ive used the AC more frequently that usual due to the heat & rainy weather, but not to the point of such a significant mpg reduction from the approximate 38mpg it should be getting. I drive a bit peppy at times but not flooring it constantly to wear excess gas consumption would be expected. I also roll long distances before having to brake. It drives very smoothly & accelerates effortlessly. Below is a list of some maintenance & mods it has.

    - new NGK plugs & wires
    - new OEM cap & rotor
    - K&N air filter
    - SI rims
    - new AC compressor
    - RSX-S exhaust
    - no heavy cargo
    - '02 Insight seats that are lighter than stocks
    - Tein springs & Koni shocks
    - poly-filled engine torque mount

    Any suggestions & theories are gladly welcomed.
     
  2. Blood_Shot

    Blood_Shot Banned Registered VIP

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    has this been going on for awhile or just your last tank?

    how many miles on it now?

    s**t my z6 just clicked over 272xxx and still gets 33mpg
     
  3. Kensai

    Kensai ♪♫♪♫♪~ Registered VIP Registered OG 5+ Year Member

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    Proper tire pressure could probably bump that number a bit...
     
  4. Blood_Shot

    Blood_Shot Banned Registered VIP

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    who's? mine is more driving habits (windows down, 80mph, mixed city/highway)
     
  5. JohnS.

    JohnS. BANGARANG Registered VIP Registered OG 5+ Year Member 10+ Year Member

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    I would ask if there's a CEL or any hesitation but you said, "It drives very smoothly & accelerates effortlessly". If the car is idling, accelerating and driving perfectly, I would say it's your A/C usage. Check your tire pressure too as mentioned.

    My 99 EX with 222k still gets 35-37. I could probably get more since all my driving is city.
     
  6. IACivicSi

    IACivicSi New Member

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    Weather can affect it as well
     
  7. JohnS.

    JohnS. BANGARANG Registered VIP Registered OG 5+ Year Member 10+ Year Member

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    The OP lives in Florida. Unless it's been in the 20's or 30's lately, the weather shouldn't be effecting the car that much. Only when it gets really cold and the car takes much longer to warm up should weather really come into play. It's been in the 40's here in the morning and I'm still getting the same mpg as when it was 90 out several months ago.
     
  8. HeX

    HeX Authoritah, respected. Staff Member Registered VIP 5+ Year Member

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    its been this way since I bought 9 months ago.

    ive seen no considerable change with any tire pressure differences.

    I drive with the windows down all the time, but i mostly drive city, so that wont impact it heavily. I stay between 40-50mph usually. I dont rev too high or excessively slow either.

    No CEL codes. Speedometer was busted for a while, but its been replaced. Still gettin around the same 250 a tank.

    Im in Miami, so its always over 88. But its been raining alot so Ive used the AC more than I normally would. Even if I cranked the AC all the time, I dont think it should do less than 35mpg considering Im not an aggressive driver.


    Any HX owners out there have any comments? I know these engines can behave differently than the usual civic models. Maybe theres sumtn Im overlooking that Im not familiar with.
     
  9. civic98ek

    civic98ek New Member Registered VIP

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    check your o2 sensors because i was missing one and my gas mileage was TERRIBLE.
     
  10. Mr.Baker

    Mr.Baker Mr. Search Registered VIP 5+ Year Member

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    If it was missing, wouldn't the CEL come on?
     
  11. reichbc

    reichbc "Brandon"

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    Yes. It would be reporting a low voltage situation.

    OP, maybe your ECU? Try resetting it. Pul lthe ECU fuse for 5-10 minutes, let it build up its mapping again.

    =)
     
  12. Cobl18

    Cobl18 New Member Registered VIP

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    I have to push my civic to get 280 miles to a tank, i usually get really close to e at 240. but i have a O2 sensor out.
     
  13. 2slo4u

    2slo4u wait4me Registered VIP Registered OG 5+ Year Member 10+ Year Member

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    AC while its raining? dang here in Washington we have the heat blasted to max when raining and AC when it reaches the high..usually low to mid 60's :P

    not really sure what the problem can be...i get about 480km in my turbo civic

    tire choice can play a roll, si wheels are heavier than hx's, at what speed to you cruise at on the freeway comes to factor, driving habits, unless you drive each gear like the manual says to and keep it at 60 on the freeways, your mile per gallon will be different than sticker
     
  14. dj_hallucn8

    dj_hallucn8 "to punish and enslave" Registered VIP 5+ Year Member

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    Yea the CEL would come on, having same issue, still need to change my pcv valve, tps & map sensors are next.
     
  15. Mr.Baker

    Mr.Baker Mr. Search Registered VIP 5+ Year Member

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    Not me.
    I usually hit the halfway mark at 150-160, but can easily pull 320-330 out of a tank. I've pulled 367 from it once.
     
  16. Trekk

    Trekk New Member Registered VIP

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    How many miles are on it? If it is a lot the O2's might be going out. The more carbon that gets on them the less effective they are.
    I know with an HX the rear O2 isnt priced too bad, but the front one can cost some coin. The HX also has an EGR valve, that could maybe give a problem but that should trip a cell. The FPR could be bad also.
     
  17. HeX

    HeX Authoritah, respected. Staff Member Registered VIP 5+ Year Member

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    The heater is hardly ever used in Miami.

    I understand heavier rims can play a roll, but SI rims are maybe 5-6lbs heavier at best. I have been trying to drive more within the manuals recommended specs for highway driving, but i still dont think it should merit such a huge drop in MPG. HX's roughly get 46+mpg hwy. So unless the HX engines are very tempermental with precise driving conditions, i still cant accept 10-20mpg drop. I dont drive like a teenage douchebag. lol
     
  18. quietfly

    quietfly New Member

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    I have a 97 DX and i'm getting around 430 per tank and average just over 39mpg. Air pressure in tires is huge, so is alignment, also check your plug gapping. i've found actually going down from 44, to 42, has made a nice difference in mid range torque. I also agree with pulling your ECU and letting it rebuild the map. also for craps and giggles check your fuel filter, as well as clean and re oil your K&N.
     
  19. HeX

    HeX Authoritah, respected. Staff Member Registered VIP 5+ Year Member

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    Regarding the plug gapping, how'd it affect your mpg? I think my ECU was recently reset, but I may do it again.
     
  20. OTiS133

    OTiS133 ... Registered VIP 5+ Year Member

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    my z6 gets roughly 29-30. iv replaced fuel filter, air filter, plugs and wires, dizzy cap and rotor, pcv valve, and ignition coil. im running 10w30 mobil1 fully synthetic oil with k&n oil filter. tire preassure is within 1 or 2 psi of recommended for tires. shifting between 3 and 4.5k rpm. i have bad valve seals. 146k miles. stock sol si wheels. aftermarket exhaust and header, with no cat converter.does this sound about right? i think it should be more but idk. also i dont use the ac and i do use the heat in the mornings to clear my windshield and get warm.


    sorry to threadjack op. i didnt wanna make a new thread asking pretty much the same thing.
     


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