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Wretched gas mileage?

Discussion in '1st Gen Tundras (2000-2006)' started by Need to know stuff, Dec 7, 2018.

  1. Dec 7, 2018 at 10:04 AM
    #1
    Need to know stuff

    Need to know stuff [OP] New Member

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    So, I'm getting about 8-10 mpg and the only hint I have to why is that my check engine light was on. I checked it out eith OBD2 and the only code it threw was about bank 2 catalyst. Which is the second catalytic converter. I read up a little bit about this code and it seems that it could be carbon buld up on the O2 consors.

    Also when I'm idling it seems to run a little rough but is not throwing any codes for any misfires.

    Also when I started it up this morning and forgot something in the house and come back it was dripping liquid (didn't check if it was gas or not)

    20181207_073404.jpg
     
  2. Dec 7, 2018 at 10:10 AM
    #2
    Festerw

    Festerw New Member

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    More than likely just condensation from the tail pipe. Change all 4 oxygen sensors, new plugs, and clean the MAF sensor. Then check your mileage.
     
  3. Dec 7, 2018 at 10:23 AM
    #3
    15whtrd

    15whtrd Mr. Blonde

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    Yeah start with the O2 sensors and go from there. Not a bad idea to change the plugs as it’s fairly inexpensive. And it’s possible they could be out of spec if it’s been running bad for a while. My Sequoia was throwing a code 1 rear O2 sensor. I replaced both and the light went away as well as the truck ran much better.
     
    aperezsh and OR18TRD like this.
  4. Dec 7, 2018 at 2:39 PM
    #4
    Professional Hand Model

    Professional Hand Model Fred Brookes

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    I’m getting 9-12 mpg city with my 2002 V8 SR5 and my engine is at perfect optimization right now. 160k miles. Without detailing everything, she has been tuned to perfection. Highway 16-18.285/75/r16
     
  5. Dec 7, 2018 at 4:45 PM
    #5
    Darkness

    Darkness New Member

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    No need to change all 4, that's expensive. Change just the bad one out. See if that helps before doing other expensive stuff.

    Do free/cheap stuff. Clean or replace air filter, clean MAF sensor, clean throttle body plate, change spark plugs. Check tire pressure. That's unusually low gas mileage.
     
  6. Dec 8, 2018 at 6:13 PM
    #6
    Need to know stuff

    Need to know stuff [OP] New Member

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    I'll do the cheap stuff at first, spark plugs, cleaning ect. Maybe have a mechanics opinion on it.
     
  7. Dec 9, 2018 at 6:45 PM
    #7
    Lost Highway

    Lost Highway New Member

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    It would be helpful to know the number of miles on that low mpg truck, it would also be good to know if you are a lead foot or a light footed driver?

    If you are going to go the cheap route, you will most likely spend more time under the hood than you can afford, and still not save any money. If one o2 sensor is bad the others aren't far behind, so how many times do you want to jack that truck up and climb under it.
     
    15whtrd likes this.
  8. Dec 9, 2018 at 6:56 PM
    #8
    15whtrd

    15whtrd Mr. Blonde

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    Along the lines of my thoughts. I had a light come on and it was the right bank downstream O2 sensor. Decided to change both downstream 02 sensors. Left the upstream ones alone. It’s been fine for a year. Now that I think of it... it could’ve been the upstream sensors.
     
  9. Dec 12, 2018 at 11:40 PM
    #9
    Rkcruza

    Rkcruza New Member

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    8-10mpg! Definitely not happy...the worst I've ever seen with my 02 Tundra is 10 and that was doing 75 with my FJ40 on a trailer and the truck pretty well loaded. Normally about 15-16 loaded for work and 17ish if I drive 55 (can't do that).
     
  10. Dec 14, 2018 at 7:28 AM
    #10
    FirstGenVol

    FirstGenVol Many ideas, few dollars

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    The one downside to the 4.7L is the abysmal MPG. No matter how passive I drive, I get about 14.8MPG. I'd be thrilled to get 20MPG like some of the newer trucks but then I'd have to pay $40K for a new truck. It is what it is.
     
  11. Dec 15, 2018 at 5:45 PM
    #11
    Theosce

    Theosce New Member

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    Rock cruiser how are you getting such good mpg? My 2007 5.7 110k miles only gets 10-12. Running stock tires at 35-40psi. Average speed is 17 mph according to my truck
     
  12. Dec 15, 2018 at 8:13 PM
    #12
    206danebmx

    206danebmx New Member

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    That sounds a little low, are you doing a lot of city driving?

    I seem to get around 12mpg in the city and average around high 14's with 35's and about 60%highway 40% city driving. I have a doublecab 4WD.
     
  13. Dec 15, 2018 at 9:40 PM
    #13
    Theosce

    Theosce New Member

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    90% city, I'm due for tranny fluid, differential fluid too. Hopefully Ill see some improvement
     
  14. Dec 17, 2018 at 5:34 PM
    #14
    Lost Highway

    Lost Highway New Member

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    I believe part of the mileage issue that everyone is seeing is that now days there is to much alcohol in the mix, it really hurts mileage and performance, it wasn't so when our trucks were new. Because of this I don't buy ARCO gas, ever, and I am willing to pay a little more for gas that limits its alcohol content.

    BTW, Theosce, make sure when you change that differential oil, you also put the limited slip additive in too.
     
  15. Jan 1, 2019 at 1:41 PM
    #15
    tacoguybill

    tacoguybill The Burrito Bandido

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    Trying to bring this one back a bit, has anyone done any modifications to successfully improve MPG? Living in FL right now it’s tolerable but looking to move back to California in the next year or so where 12-13 mpg just ain’t gonna cut it.
     
  16. Jan 1, 2019 at 6:39 PM
    #16
    206danebmx

    206danebmx New Member

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    The ethanol in the gas could improve it, but I've read it's only around a 2% improvement, so from 12mpg to about 12.25 mpg, not much improvememt. Also finding ethanol free gas is challenging at least for me in the seattle area. I am going to try just for kicks and see if it helps. It may also be more expensive than typical gas so possibly a wash in the end.

    Driving 55mph when on the freeway should help improve mpg.
     
  17. Jan 1, 2019 at 8:30 PM
    #17
    careyrob

    careyrob New Member

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    Don't worry about the water coming from the exhaust. The two largest products of combustion are carbon dioxide and water. When your engine and exhaust are hot the water remains steam. When they're cold you'll see a little water drip.

    Bank 1 and Bank 2 refer to the right and left sides of the engine. For V8s each bank has 2 sensors. O2 sensor 1 is located before the 1st cat and sensor 2 is after the 1st cat. A bad 2nd cat doesn't result in any O2 trouble codes since there is no sensor downstream from it.

    Contrary to what dealerships and auto parts stores want you to believe initially an O2 sensor code doesn't usually mean the sensor is bad. It means that the computer is getting an O2 sensor reading it doesn't expect based on the assumption that all the other sensors and systems are functioning properly. But if ignored long enough the original problem may eventually cause the O2 sensor to fail also.

    I commonly hear people say that a faulty O2 sensor was "carboned up" to supposedly explain why it failed. Most people somehow overlook the next most reasonable question which is , "Why is the sensor carboned up?"

    Even if the sensor has gone bad just changing it doesn't fix whatever is at the root of the problem.

    If you have over 150k miles on the engine and your regular maintenance is current it could need a fuel injection system service to clean the throttle body, IAC valve, EVR valve, intake manifold, injectors, the backs of the intake valves and the combustion chambers. It has to be a real fuel injection service though, not the single bottle of fuel injector cleaner from the auto part store. A quality FI service can restore some of your previous fuel mileage performance if it's not what it used to be.
     
    Last edited: Jan 2, 2019
    bmcdds likes this.
  18. Jan 1, 2019 at 9:15 PM
    #18
    bmf4069

    bmf4069 New Member

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    Move to TX. Gas is under $2 a gallon here! ;)
     
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