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Terrible gas mileage

Discussion in 'Care & Maintenance' started by Hummer, Apr 11, 2011.

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    Hummer Well-Known Member

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    I dont know if this is the right thread but whatever, so I've been getting terrible gas mileage lately, i fill up my car to half way, drive across town to a friends house and back (mostly back roads not many stops) and by the time i get home, swing by the gfs (who lives pretty close) and back im almost on empty. It's ridiculous, for the most part i baby my car unlike some people who like to pass cars in one lane roads on hillside curves *ahem* COROLLAGT *ahem* (bastard almost got us killed) I'm wondering if you guys can list some stuff i can check aside from the obvious.

    guess im gonna check the spark plugs, air filter, and check for any leaks.
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    1337Rolla oh my

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    tire pressure, maf sensor covered in garbage.
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    fishexpo101 Get Some

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    What's the mileage of the car?
    Any recent repair work or new parts installed?
    Any new additives you were trying out?
    What sort of mileage decrease are we talking about - 10% sort of drop, like going from 33MPG to 30MPG or we talking 50% or more?

    Mileage fluctuations of 5-10% are more or less in the noise, 10-15% or more is common with winter blended gasoline (summer blends are being reintroduced to stations starting in March). But if you see a consistent 20-25% or more decrease, likely be something mechanical and/or electrical.

    If it started suddenly and nothing else was changed on the car, could be a case of a lazy or dying O2 sensor. O2 sensor can degrade enough to not work correctly, but not completely fail, as to set a CEL.
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    roachrolla Hipster

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    I was getting like <20mpg but then I cleaned my air filter and mpg improved dramatically.
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    Hummer Well-Known Member

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    I really do need to check the tire pressure, good idea. The car has 123XXX miles on it, other than changing the transmission oil and differential oil no other maintenance was done except tie rods being replaced but I dont think that should affect gas mileage. About 15% seems right, and the car has no MAF sensor, dont let the front end fool you, its a 99.
    Added: Apr 11, 2011 6:49 PM
    Thought sometimes when I accelerate I can smell either gas or oil from the hood, I dont know if im smelling things or its from another car or what.
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    its_ikon FIRST widebody

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    might have been mentioned, but have you done a major tune up?
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    Hummer Well-Known Member

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    Nope, but I need to hopefully this weekend. Gonna clean the air filter today its just a pain in the ass to get to.
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    its_ikon FIRST widebody

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    at 123k miles i would definitely check everything from the throttle cable to the exit of the exhaust. make sure you're not smoking out the exhaust which could be a sign of other problems.
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    MacktasticSlick TRD whore with 36,000 posts, bitch

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    I should follow this thread, but I'm sure my mileage is related to the p0446 code my car is throwing out. Still helpful though.
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    KrypticKarma ~2001 Corrizm~

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    You mentioned you did tie rod ends recently? You did get an alignment right?? If not you're toe might be out of adjustment and not only will it eat the tires.. but it will kill your fuel mileage also.
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    Hummer Well-Known Member

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    Yeah, of course i got a 4 wheel alignment.
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    MacktasticSlick TRD whore with 36,000 posts, bitch

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    I'm wondering how a slight alignment problem will tank your gas mileage that bad.
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    Hummer Well-Known Member

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    Try running with your feet pigeon toed next time, thats how.

    Also today while inspecting the engine bay I discovered my CAI piping had come undone at the throttle end because the battery was pushing up against it. So I re-arranged my battery and secured it better so it wouldnet wobble into it and push the intake end piping off. All of the clamps I had were too small to fit around so I'll have to purchase one to make sure it never comes loose again. Doubt thats the reason for my mileage but I also filled up my tires today and my gas tank, will see how things go in the coming days.
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    CorollaGT Low & Slow

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    Im pretty sure it does have a MAF...... ? Should be hooked up to your intake...
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    MacktasticSlick TRD whore with 36,000 posts, bitch

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    No they added a MAF sensor in 2000, when they added vvt, the 98 to 99 has a MAP sensor.
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    CorollaGT Low & Slow

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    huhh, interesting. where is the map sensor located? and would the maf be where the map used to be?
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    MacktasticSlick TRD whore with 36,000 posts, bitch

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    The MAP sensor I assume is in the same position as the newer MAF sensor... In my car the MAP sensor is the little plastic pointy one that goes in the back of the stock airbox, but I don't see how it even does anything, because with my aftermarket intake, I let the sensor just hang down in the engine bay, and it didn't throw a CEL... something you can't do with the newer MAF-equipped cars.
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    CorollaGT Low & Slow

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    Oh, I made a hole in my intake for that sensor. I figured it probly needed it for the proper fuel mix. that might be why you have crappy gas mileage.
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    MacktasticSlick TRD whore with 36,000 posts, bitch

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    Well right now I'm running the stock box because of CA smog testing, so that wouldn't be it. Back when I had the CAI and the sensor just hanging there (also before the CEL came on) I could squeeze out 40mpg on the freeway if I wanted to, now it's just garbage. I think I'm gonna get under the car today and check out the vacuum switching valve.
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    CorollaGT Low & Slow

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    But dont forget to take lots of pics from them drop.lol AND POST THEM ALREADY!!!!!!
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    MacktasticSlick TRD whore with 36,000 posts, bitch

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    calm down my son, it'll all be over soon.
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    Hummer Well-Known Member

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