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  1. #1

    Default What's the best way to tell if you've picked up some bad gas?

    The other day a friend put 30 gallons of "the good stuff" in my tank. The one time I've put in Supreme, it got an occasional miss and ran slightly rough, so I stay away from it.

    The next morning after this fill up, while sitting at a light, it began running really rough, and the check engine light started flashing.

    Starts fine, but runs rough.


  2. #2



    Prob water if the fuel was bought at an admirals


    .....ya clock faster and faster till the desire for speed overcomes the fear of bus.....

  3. #3


    Shell. But it's a station in town that doesn't get as much traffic as the others. I'm guessing that, plus it's higher octane, means it's probably been sitting in the ground a lot longer than the less expensive gas.

    If I want to syphon as much out as possible, would one of those Shaker Syphons work? Or it there a screen in the tank filler tube?

  4. #4


    a flashing engine light is not a good thing. I believe that it indicates a misfire condition and can damage your cats. If the light is still flashing I would not drive it.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  5. #5


    It's sitting.

    From what I'm reading, it's possible to syphon most of the fuel out. I'm going to get some different fuel in her and see what happens.
    If that doesn't do it then it's off to the shop.

  6. #6


    Well it's not bad fuel. Changed the gas filter and while it was off I pumped out half the tank. Started it up and ran some Seafoam down the intake. Noticed a small puddle of what I assumed was water at the tailpipe and didn't think much of it. Until this morning when it had rained and that puddle appears to be unburned fuel.

    Off to the shop on Wed.

  7. #7


    looked around and found maybe bad injector,timing or fouled plugs, hope it won't be too bad for ya.

  8. #8


    Yeah, I figured injector at first, but now I'm thinking it's spark since the gas is getting pushed on down the line.
    Had the intake manifold gasket done a month ago, and I asked if they thought it'd be a good idea to switch out the distributor gear while we were at it. They said it was fine.'s......that....gear....I...will....bec ome.....quite...disenchanted........

  9. #9


    Yeah, I always get fuel at the busiest station, just to keep it filled with the freshest fuel I can get. For me, that's the local truck stop. Higher octane fuel requires more effort to burn, and later model engines have less tollerance for bad fuel. Could be the pump got clogged as well. I hope it's easy and cheap for ya.
    Brian L.

    Brian Larson CST. KC9DAK.
    Janesville WI.
    87 GMC G20 6.2 diesel.

  10. #10


    Not good. Compression in #2 very low. Taking a valve cover off today to see what we can see.

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