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

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Naptime, May 30, 2012.

  1. Naptime

    Naptime Rockstar 100 Posts

    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. NagRuTan

    NagRuTan Rockstar


    Prob water if the fuel was bought at an admirals :rofl:

  3. Naptime

    Naptime Rockstar 100 Posts

    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. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    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.
  5. Naptime

    Naptime Rockstar 100 Posts

    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. Naptime

    Naptime Rockstar 100 Posts

    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. JnBama

    JnBama Rockstar 4 Years 500 Posts

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

    Naptime Rockstar 100 Posts

    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.

  9. RallySTX

    RallySTX Member 100 Posts

    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.
  10. Naptime

    Naptime Rockstar 100 Posts

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

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