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Discuss catalitic problems??? in the alt.autos.gm forum at Car Dealer Forums; i have a 94 grand prix and just changed a timing belt on it.it's the ...
  1. #1
    robert -wanda fox
    Guest

    Default catalitic problems???

    i have a 94 grand prix and just changed a timing belt on it.it's the 3.4
    dohc engine.problem now is it ran fine for about 10 minutes then upon it in
    idling, i gave it some gas by way of pulling on the throttle under the hood
    and there appeared to be a loud hiss from the front of engine then and
    engine started to idle roughly,the cat also is making a lot of noise, like
    it's all broken up inside,it wasn't this bad before belt went.but i had test
    run the car several times adjusting timing belt aand it ran several times
    with cams out of time,if the cat was going bad to begin with,could the
    engine out of time running really destroyed it????just what are the signs of
    a bad cat????what was the hiss then rough idle????is the cat bolted up to
    where i can replacwe myself???



  2. #2
    Shep
    Guest

    Default Re: catalitic problems???

    Um, get underneath and see if you can get to it. Put a vacuum gage on the
    engine see if it drops way off under power, indicating possible clogged cat,
    or put a exh. back pressure gage in the o2 port, 1.5 to 2.0 psi max.
    "robert -wanda fox" <res0ta8b@verizon.net> wrote in message
    news:Am8Fg.13342$9v1.8412@trnddc07...
    >i have a 94 grand prix and just changed a timing belt on it.it's the 3.4
    > dohc engine.problem now is it ran fine for about 10 minutes then upon it
    > in
    > idling, i gave it some gas by way of pulling on the throttle under the
    > hood
    > and there appeared to be a loud hiss from the front of engine then and
    > engine started to idle roughly,the cat also is making a lot of noise, like
    > it's all broken up inside,it wasn't this bad before belt went.but i had
    > test
    > run the car several times adjusting timing belt aand it ran several times
    > with cams out of time,if the cat was going bad to begin with,could the
    > engine out of time running really destroyed it????just what are the signs
    > of
    > a bad cat????what was the hiss then rough idle????is the cat bolted up to
    > where i can replacwe myself???
    >
    >




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  3. #3
    Todd A. Delk
    Guest

    Default Re: catalitic problems???

    Well, the hissing sounds like to me a vacuum leak. As for the cat, if you
    hear a rattle noise from it and you checked your exhaust to make sure there
    are no broken wields or broken mounts then I would have it replaced.Very
    expensive. The cat is hard to replace.You will have to disassemble the
    exhaust. Most cats are mounted behind the engine right under the passenger
    floor board.As for the timing, if it is off too far you can damage the
    cylinders and it will run very bad.I hope this helps.Good luck.

    --
    Todd A. Delk
    "robert -wanda fox" <res0ta8b@verizon.net> wrote in message
    news:Am8Fg.13342$9v1.8412@trnddc07...
    >i have a 94 grand prix and just changed a timing belt on it.it's the 3.4
    > dohc engine.problem now is it ran fine for about 10 minutes then upon it
    > in
    > idling, i gave it some gas by way of pulling on the throttle under the
    > hood
    > and there appeared to be a loud hiss from the front of engine then and
    > engine started to idle roughly,the cat also is making a lot of noise, like
    > it's all broken up inside,it wasn't this bad before belt went.but i had
    > test
    > run the car several times adjusting timing belt aand it ran several times
    > with cams out of time,if the cat was going bad to begin with,could the
    > engine out of time running really destroyed it????just what are the signs
    > of
    > a bad cat????what was the hiss then rough idle????is the cat bolted up to
    > where i can replacwe myself???
    >
    >




  4. #4
    bob
    Guest

    Default Re: catalitic problems???

    What about removing it? Or if you have air care, put a pipe down the
    middle of it....problem solved


    In article <Am8Fg.13342$9v1.8412@trnddc07>, res0ta8b@verizon.net says...
    > i have a 94 grand prix and just changed a timing belt on it.it's the 3.4
    > dohc engine.problem now is it ran fine for about 10 minutes then upon it in
    > idling, i gave it some gas by way of pulling on the throttle under the hood
    > and there appeared to be a loud hiss from the front of engine then and
    > engine started to idle roughly,the cat also is making a lot of noise, like
    > it's all broken up inside,it wasn't this bad before belt went.but i had test
    > run the car several times adjusting timing belt aand it ran several times
    > with cams out of time,if the cat was going bad to begin with,could the
    > engine out of time running really destroyed it????just what are the signs of
    > a bad cat????what was the hiss then rough idle????is the cat bolted up to
    > where i can replacwe myself???
    >
    >
    >


  5. #5
    Paul
    Guest

    Default Re: catalitic problems???

    A good blast down the highway should clear the cat of any fuel
    residue. A new Monolith cat is fairly cheap = hundreds less than dealer
    item, so to speak.

    The rough running could be a vacuum leak, or similar pesty problem
    Some cars use an air reaction system to keep cat hot by supplying
    bonus oxygen via a belt driven pump. The hiss could be compressed air ?


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