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    Thread: Symptoms of a bad catalytic converter

    1. Member DaveLinger's Avatar
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      11-02-2008 07:13 PM #1
      I'm not going to ask WHAT the symptoms are of a bad catalytic converter; I googled it and have found the following:

      Here are just a few of the signs and symptoms of a plugged/dead cat:

      1. Markedly decreased low rpm power,
      2. Engine runs a little hotter than normal at constant cruising speeds,
      3. Exhaust leaks near header that won't seal in spite of new gaskets,
      4. Bucking or hesitation while accelerating,
      5. Cat's exterior surface temp cooler near outlet.

      And that seems like the exact problem I'm having with my car. And it has no extra CELs, so I don't think it's an 02 sensor; and I logged my MAF, intake air temp, etc. in VAG-COM and it all looks fine.

      So I'm planning on hollowing out my cat on Tuesday to see if that fixes the problem.

      However, until then, what can I log on VAG-COM to verify or disprove that the cat is the problem?


    2. Member themandillon's Avatar
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      11-02-2008 07:15 PM #2
      ive never had a bad cat in a mk3 before, but in my mkiv i had a cel specifically for catalyst eficiency below threshhold i think when my cat went bad.
      Quote Originally Posted by Louie Bricants View Post
      I also don't see how Bags=Stance. Technically the car is sitting not standing.

    3. Member DaveLinger's Avatar
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      11-02-2008 07:17 PM #3
      Quote, originally posted by themandillon »
      ive never had a bad cat in a mk3 before, but in my mkiv i had a cel when my cat went bad.

      I suppose it could depend on the setup; I'm running a chip which ignores the missing SAI and the downstream o2 sensor (which is why I won't get a CEL even with a test pipe), but I ran my OEM chip for a couple of days and it never threw a code.

      I know a code exists for "catalyst efficiency below theshold", but maybe that only applies to certain malfunctions of the cat.


    4. Member magics5rip's Avatar
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      11-02-2008 07:20 PM #4
      Yup, sounds like a bad cat to me. The sure fire sign that its not letting anything through is that you are getting leaks through your exhaust manifold. My car had the same problem, except I was turbo and couldn't build boost...probably blew every gasket from the engine to the cat before figuring it out.

    5. Member DaveLinger's Avatar
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      11-03-2008 12:20 AM #5
      How's this for a symptom of a bad cat? This is after driving maybe 10 miles:

      Sorry there's no color; trust me, it was bright red; practically lit up the whole parking lot.


    6. Member iamnotemo's Avatar
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      11-03-2008 12:27 AM #6
      haha, yes your cat is toast.

    7. 11-03-2008 12:32 AM #7
      gutting a cat is a pain or atleast i had trouble with it ive herd to use a torch and it helps

    8. Member DaveLinger's Avatar
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      11-03-2008 12:33 AM #8
      I've heard that it's not very difficult, but I do have a torch handy if needed.

    9. 11-03-2008 12:34 AM #9
      Getting a rusted cat off the car is a pain in the ass.

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      11-03-2008 12:39 AM #10
      Quote, originally posted by DeeevO »
      Getting a rusted cat off the car is a pain in the ass.


      i had to cut mine of before the flange on the downpipe. and i had to cut the pipe after the cat flange.

      Quote Originally Posted by rlsib16 View Post
      as for me, the worst ive been caught doing was crashing and almost flipping golf carts at a town park i worked at. that high center of gravity catches you offguard sometimes.

    11. 11-03-2008 12:44 AM #11
      useful info here. thankyou Davelinger

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      11-03-2008 12:48 AM #12
      My cat rattles, and my car stinks like an 70's v8, raw unburnt fuel smells nasty. I've been driving like this for over a month, and it's starting to get worse. I need a cat and an O2

    13. Member magics5rip's Avatar
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      11-03-2008 07:48 PM #13
      Might as well go with a magnaflow high flow from performance peddler; costs less than an OEM one anyway. I think i paid $110 shipped. Some have claimed you can get them for less than that.

    14. 11-03-2008 08:11 PM #14
      Hollowing out your cat takes a large prybar and about 20 minutes of poking with attitude. Getting it off to probe at may take a little longer.

      PAtrick


    15. 11-03-2008 08:17 PM #15
      Quote, originally posted by Blown Wide Open »
      Hollowing out your cat takes a large prybar and about 20 minutes of poking with attitude. Getting it off to probe at may take a little longer.

      PAtrick


      What he said, instead it only took five minutes from my friend who is a 145 lbs. soaking wet.

    16. Member redskinsboy326's Avatar
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      11-03-2008 08:57 PM #16
      sawzall. **** does work.

    17. Senior Member Dan J Reed's Avatar
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      11-03-2008 09:10 PM #17
      Its important to point out... its against the law to remove them...

      And when they are glowing like that - its not the "converter" that broke, but rather something else that caused the converter to sinter/melt down.. IE - running rich.

      Too much fuel, not enough air in there...

      Bad coil
      Stuck open Injector
      Bad Plug
      IAT/ECT/TPS/MAF sending too rich signal
      Ripped fuel pressure regulator causing fuel to be sucked into the intake...


    18. Member
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      11-03-2008 11:12 PM #18
      Quote, originally posted by Dan J Reed »

      Bad coil
      Stuck open Injector
      Bad Plug
      IAT/ECT/TPS/MAF sending too rich signal
      Ripped fuel pressure regulator causing fuel to be sucked into the intake...

      bad timing did mine in.
      quick.
      Quote Originally Posted by rlsib16 View Post
      as for me, the worst ive been caught doing was crashing and almost flipping golf carts at a town park i worked at. that high center of gravity catches you offguard sometimes.

    19. Member sickgixxer69's Avatar
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      11-03-2008 11:18 PM #19
      Its easy to gut it. Just hard to get it off. I used a big long screw driver and a hammer to hit it with.

    20. Member magics5rip's Avatar
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      11-09-2008 03:57 PM #20
      Quote, originally posted by Dan J Reed »
      Its important to point out... its against the law to remove them...

      its also illegal to gut them. i ran one for about 6 months, got tired of the back fires and exhausty smell till it warmed up. High flow keeps you legal, keeps the environment a little happier too.


    21. 11-09-2008 04:08 PM #21
      ...or depending on where you live....just run with out one. i dont have emissions where i live and run a race header and no cat.

    22. Member justin_6649's Avatar
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      11-09-2008 06:11 PM #22
      Quote, originally posted by Golf2go »
      ...or depending on where you live....just run with out one. i dont have emissions where i live and run a race header and no cat.

      wow your carbon foot print must put 572's to shame


    23. Member relmonte's Avatar
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      11-09-2008 06:39 PM #23

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