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2012 FJ terrible mpg

Discussion in 'FJ Cruisers' started by fd_geoff, Jan 20, 2019.

  1. Jan 20, 2019 at 9:17 PM
    #1
    fd_geoff

    #1
    fd_geoff [OP] Member

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    2012 FJ Cruiser Trail Teams
    Alumitec Front Bumper, Baja Roof Rack, LED Light Bar, 12,000lb winch, King Coilovers, 31" BF Goodrich All Terrains, Boztec Skid Plates, Ham Radio, On-board Air Compressor, Rear Facing Flood Lights, Dual Battery, Baja Snorkel
    Hey all. Recently I've found out that my FJ is getting really bad mpg(100 miles to the tank on Highway, less on city streets; just drove it 20 miles from full and ended up a little under 3/4 of a tank on the freeway). I have 31" All Terrains and some added weight from modifications, but have never gotten this bad of mpg. I have heard about the thermostat failure and MAF being dirty. I will change both out tomorrow to test if that is the problem. There are no check engine lights, has 83k miles and on city streets, I usually have my tires aired up to 37psi. Also, the only problem with it so far has been the fuel pump failing at around 81k miles. Just wanted to see your guys' two cents. Happy trailing!
     
    fd_geoff, Jan 20, 2019
    #1
  2. Jan 20, 2019 at 9:23 PM
    #2
    ppham444

    #2
    ppham444 Well-Known Member

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    You don't have to change out the MAF sensor. Try cleaing it first. Make sure you use an electrical cleaning spray.
     
    ppham444, Jan 20, 2019
    #2
  3. Jan 23, 2019 at 8:16 AM
    #3
    fd_geoff

    #3
    fd_geoff [OP] Member

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    2012 FJ Cruiser Trail Teams
    Alumitec Front Bumper, Baja Roof Rack, LED Light Bar, 12,000lb winch, King Coilovers, 31" BF Goodrich All Terrains, Boztec Skid Plates, Ham Radio, On-board Air Compressor, Rear Facing Flood Lights, Dual Battery, Baja Snorkel
    Thanks. I ended up cleaning the MAF really well, change the air filter, and swap out the Thermostat. But it still is getting 3-5mpg. Any other ideas what could cause this rapid surge? All the skid plates and bumpers only add about 200-300lbs I would think. Only thing I can think of is the tires. They're old and pretty worn. Not bald but prettyclose.
     
    fd_geoff, Jan 23, 2019
    #3
  4. Jan 23, 2019 at 8:24 AM
    #4
    uurx

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    uurx Well-Known Member

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    aside from your fuel consumption

    how does the truck run? does it drive and accelerate normal??

    3-5mpg, I would assume the car runs like a bag of poop and sounds like it is really struggling to pick up and go

    after the big drop on the fuel gauge have you tried fueling it right back up to confirm the gauge is not faulty?
     
    uurx, Jan 23, 2019
    #4
    doorsidedown likes this.
  5. Jan 23, 2019 at 8:31 AM
    #5
    doorsidedown

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    doorsidedown Well-Known Member

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    damn! 3-5 mpg? Something is definitely wrong. 300lbs of armor wouldn’t do that.
     
    doorsidedown, Jan 23, 2019
    #5
    Wixo likes this.
  6. Jan 23, 2019 at 9:25 AM
    #6
    fd_geoff

    #6
    fd_geoff [OP] Member

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    2012 FJ Cruiser Trail Teams
    Alumitec Front Bumper, Baja Roof Rack, LED Light Bar, 12,000lb winch, King Coilovers, 31" BF Goodrich All Terrains, Boztec Skid Plates, Ham Radio, On-board Air Compressor, Rear Facing Flood Lights, Dual Battery, Baja Snorkel
    The truck actually runs pretty decent. It feels sluggish sometimes and I do smell quite a bit of raw gas out the exhaust. I'm thinking I may have a faulty O2 sensor that's fouled or something but not throwing a code. Toyotas are weird when they break because usually they never break. Haha.
     
    fd_geoff, Jan 23, 2019
    #6
  7. Jan 23, 2019 at 9:26 AM
    #7
    fd_geoff

    #7
    fd_geoff [OP] Member

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    2012 FJ Cruiser Trail Teams
    Alumitec Front Bumper, Baja Roof Rack, LED Light Bar, 12,000lb winch, King Coilovers, 31" BF Goodrich All Terrains, Boztec Skid Plates, Ham Radio, On-board Air Compressor, Rear Facing Flood Lights, Dual Battery, Baja Snorkel
    That's what I was thinking. Usually you need +750lbs of added weight to seriously affect mpg.
     
    fd_geoff, Jan 23, 2019
    #7
  8. Jan 23, 2019 at 9:29 AM
    #8
    willie64

    #8
    willie64 Willie64

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    144 watt led lights on front 36 watts x2 led on the back, cb, Kenwood ham, icon 3" lift, 285/75/16 Fierce Attitude tires, JoeZilla sliders, 4x innovation rear bumper, ARB front bumper. Snorkel. On the workbench: more stuff I can't afford.
    I'd change the 02 sensors and have the cats checked. (Do you have one or two? ) I've read that if the cats go out it can cause havoc on the mpg's.
     
    willie64, Jan 23, 2019
    #8
  9. Jan 23, 2019 at 12:10 PM
    #9
    Taco Dan

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    Taco Dan Well-Known Member

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    I get around 14.5 city mpg with my 07 fj, front steel bumper with winch, 33" e-ply tires, sliders. You sound like your engine is running extremely rich. and you're not throwing any codes?
     
    Taco Dan, Jan 23, 2019
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  10. Feb 7, 2019 at 7:18 PM
    #10
    Rparker017

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    Rparker017 Well-Known Member

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    I would also recommend cleaning the throttle body when you clean the MAF sensor. It will help with MPG, but isn’t the source of your problem if you’re only getting 3-5 mpg!

    FJ typically throws codes like crazy when sensors or cats are bad.
     
    Rparker017, Feb 7, 2019
    #10
  11. Feb 28, 2019 at 6:38 AM
    #11
    victoriabam

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    victoriabam New Member

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    Its nice to read everyone opinion about FJ's.
     
    victoriabam, Feb 28, 2019
    #11
  12. Jul 15, 2019 at 4:20 AM
    #12
    abqnurse80

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    abqnurse80 Well-Known Member

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    Bilstein 5100 all around, first clip front. AVS window visors, BFG AT KO2s. JBL.
    abqnurse80, Jul 15, 2019
    #12
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