2004 STS running rough and making hissing noise
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Cadillac STS Forum - 2005 through 2012 Discussion, 2004 STS running rough and making hissing noise in Past Cadillac Vehicle Discussion; My 2004 STS check engine light came on about a week ago. I noticed today that there was a hissing ...
  1. #1
    kayjenrose is offline Cadillac Owners Member
    Automobile(s): STS
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    2004 STS running rough and making hissing noise

    My 2004 STS check engine light came on about a week ago. I noticed today that there was a hissing noise coming from the engine. My neighbor looked at it and said that the vacuum hose was loose. He followed a hose that was on the left side of the engine to the back and did something back there that I couldn't see. Now when I started the car, it runs rough as hell. What could this be and how much is this going to cost to repair? I'm afraid to even drive it to the mechanic to try and get it diagnosed.

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  3. #2
    Ludacrisvp's Avatar
    Ludacrisvp is offline Cadillac Owners Connoisseur
    Automobile(s): 08 STS4 V8 F55 1SG Euro tails & 01 Monte SS Pace Car
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    Re: 2004 STS running rough and making hissing noise

    Not sure, however you may get more help if you posted in the right section, if you have an 04 STS then you have a Seville (FWD - completely different beast), and if I recall correctly they didnt make the 04 STS in the USA at least so then you likely have an SLS.
    I guess I would ask the neighbor what he did to it first.

  4. #3
    C&C's Avatar
    C&C
    C&C is offline Cadillac Owners Connoisseur
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    Re: 2004 STS running rough and making hissing noise

    While there is a section (for your Seville), this question may be generic enough that your answer can be answered here; I believe you have a vacuum leak somewhere and you'll have to try and track it down by listening for it. Good luck.

  5. #4
    EChas3's Avatar
    EChas3 is offline Cadillac Owners Master
    Automobile(s): 2006 STS4 V8 1SG & 2007 STS V8 1SE
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    Re: 2004 STS running rough and making hissing noise

    As a 2004, isn't it a Seville Luxury Sedan - SLS. I think the last FWD STS were 2003 models.

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