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Thread: Aggravating Fuel Economy Problem

  1. #19
    Join Date
    Nov 2007
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    18,823

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    Quote Originally Posted by befarrer View Post
    Don't forger that the A/C system is on whenever defrost is selected to take the humidity out of the air, regardless of the temp setting.
    Depends on the vehicle. But typically true.


    Yup. All this shit adds up to decreased mileage in the winter.


    If you're one of those bastards only losing 9% economy, "shut-uppa-you-face!" and realize that us hombre's losing 25% mileage don't even bother to bitch.

    <3
    Quote Originally Posted by LOLJDM View Post
    Rob with an awesome post as always.

  2. #20
    Join Date
    Oct 2007
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    Babying a vehicle could cause increased mileage as the engine would build up carbon and not work as well. Consuming more fuel.
    1993 B2200, S4 13B Swapped, 5-speed, otherwise stock

  3. #21
    Join Date
    May 2013
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    363

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    So a problem with GM trucks and SUV's from like 99-15 is that the exhaust manifold bolts would fatigue and rust and snap off causing exhaust leaks. There is 6 bolts on each side & with my truck on the drivers side the very front and very back bolt were snapped off & on the passenger side the very front one. I got new gaskets and bolts for the exhaust & i took out the driver front broken bolt no problem with some locking pliers, the back one tho was impossible tried for hours. Then the passenger front one snapped flush with the engine so no way to take it out unless you drill it. GM knew this problem so there is these bracket/clamps they made that use pre existing holes in the block to bolt to then have a set screw to the exhaust manifold. So i bought one for the rear and one for the front. We'll see how my MPG change after taking care of these exhaust leaks, the O2 sensors should no longer be reading extra oxygen in the exhaust.

  4. #22
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    Nov 2007
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    That problem isn't specific to GMC. Same thing happens on almost every RAM 5.7L - I had to do mine around 175K I think? Just the constant heating/cooling of the bolts and then they snap. I noticed a MPG drop when it happened. And it went back to normal after I fixed it. I didn't drill out the snapped off bolts though... I had Chris weld a nut onto the end and then we just unscrewed it properly. The gaskets are cheap; $20-$30, but the new "redesigned" bolts are like $100-$150, and that's the discounted price. I was quite surprised. Perhaps they're just made of stronger steel.
    Quote Originally Posted by LOLJDM View Post
    Rob with an awesome post as always.

  5. #23
    Join Date
    Oct 2007
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    1,337

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    Its probably due to steel bolts threaded into aluminum heads holding on cast iron manifolds under extreme heat fluctuations. Different expansion rates fatiguing the bolts.
    1993 B2200, S4 13B Swapped, 5-speed, otherwise stock

  6. #24
    Join Date
    Mar 2014
    Posts
    704

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    i changed 02 sensors. coil packs. new plugs. didn't make a difference. a guy told me he could hear an exhaust leak once. I couldn't hear what he heard.

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