Melted cats

Discussion in '2005+ Mustang GT 4.6L Tech' started by Johnstone, Jun 15, 2019.

  1. Johnstone

    Johnstone forum member

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    after two weeks and a new fuel pump we finally found my problem.
    My Freaking cats were completely blocked.

    well one was blocked but I'm glad I found it.
    My car felt slow and felt like it was running lean.
    changed my fuel pump and still nothing. I will be removing them both and installing a Hpipe

    my question is, would that be why my spark plugs are black? bad carbon build up??

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  2. 759-OR

    759-OR Junior Member

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    Not what I was expecting based on the title.

    Slightly disappointed...
     
  3. 07gts197

    07gts197 forum member

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    Actually both of those could be symptoms of another problem like a vacuum leak or dirty/faulty maf.


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  4. Johnstone

    Johnstone forum member

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    what about bad tune?? I had a two-step installed and I remember racing it one night and I honestly thought my car caught fire!
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  5. 07 Boss

    07 Boss forum member

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    Describe why you thought your car was on fire.
     
  6. Johnstone

    Johnstone forum member

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    it sounded like a backfire in third gear and the smell

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  7. Pentalab

    Pentalab forum member

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    The clogged cats... were they oem, or did you have LT's, and a catted X / H mid section ? Were the cats ceramic, or metallic spun ? If running too rich, excess fuel will ignite inside the hot cats. Typ, clogged cats are indicative of too rich a mixture.. but not always.
     
  8. Johnstone

    Johnstone forum member

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    original cats.. I have borlas catbaks for my exhaust.. nothing special
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  9. 08MustangDude

    08MustangDude forum member

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    Melted cats isn't clogged cats.. There are a few causes for clogging.

    One way, is by a piece of the converter that breaks free, but is too large to escape through the rest
    of the cat, or exhaust piping, blocking the exhaust stream.

    Excessive carbon clogs them when they're not running hot enough. High carbon can also occur
    from burning oil or anti-freeze. This also goes back through the EGR further hindering performance.

    Too much fuel entering the cat, will eventually melt them. This would be from a tune with more
    fuel, and/or bad plugs not firing properly to burn it.

    Bad sensor causing lean or rich conditions that damage the cat.
     
  10. RED09GT

    RED09GT Senior Member S197 Team Member

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    It was the 2 step that killed them. The unburnt fuel will clog up them up and damage the cats.
     
  11. jewc75

    jewc75 Cant Stop, Wont Stop

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    Is this car boosted?
     
  12. Johnstone

    Johnstone forum member

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    yes it is

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  13. 06 T-RED S/C GT

    06 T-RED S/C GT forum member

    Age:
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    I'd check with whomever your tuner is. Some tuners disable the OEM safety parameters that prevent the OEM cats from potential damage. I'd also have your air/fuel checked just to make certain you're not running too lean or too rich.