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Failing Emissions - leaking manifold?

Discussion in 'Technical Q&A' started by jssans, Jun 29, 2006.

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  1. jssans

    jssans Formula Junior

    Jun 1, 2005
    839
    St. Louis
    Full Name:
    Josh
    #1 jssans, Jun 29, 2006
    I'm failing my hyrdocarbons test for emissions on my 95 F355. I have had the cats tested via heat difference & they are showing about 100 degree difference from the front to the back of the cats. Which means the cats are working properly. I have a leaking manifold on the passenger side & my hunch is that is causing the hydrocarbons to go over the test limits. Has anyone experienced the same results?
     
  2. tomberlin

    tomberlin Formula Junior
    Silver Subscribed

    Apr 9, 2005
    854
    Bethesda
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    tom berlin
    #2 tomberlin, Jun 29, 2006
    HC is unburned fuel. High HC can be caused by: Too much fuel, which causes a rich misfire; too lean which causes a lean misfire. An air leak can cause a lean misfire. An ignition fault will cause a misfire. Anything that causes poor running causes high HC.
    Cheers,
    Tom
     
  3. jssans

    jssans Formula Junior

    Jun 1, 2005
    839
    St. Louis
    Full Name:
    Josh
    #3 jssans, Jun 29, 2006
    Nice.
    Well, I'll fix the manifolds(air leak) & if it doesn't do the trick I'll work my way down the list.
     
  4. tomberlin

    tomberlin Formula Junior
    Silver Subscribed

    Apr 9, 2005
    854
    Bethesda
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    tom berlin
    #4 tomberlin, Jun 29, 2006
    Can you tell if it's idling on all cylinders? Usually air leaks affect idle first because they are limited in how much "false" air they can admit. At higher engine speeds their effect is limited. Electronic idle control can sometimes make it hard to tell if the idle is normal or not. Try spraying WD-40, or carb cleaner(my choice) around the manifold. It should tell you if you have a leak.
     
  5. jssans

    jssans Formula Junior

    Jun 1, 2005
    839
    St. Louis
    Full Name:
    Josh
    #5 jssans, Jun 30, 2006
    I'll try ur advice this Saturday with the carb cleaner. I'm barely failing the HC test. Little frustrating.
     

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