2009 3.6L STS Coil/Spark Plug replacement

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Cadillac STS Forum - 2005 through 2012 Discussion, 2009 3.6L STS Coil/Spark Plug replacement in Past Cadillac Vehicle Discussion; Just received a diagnostic stating that #4 cylinder is misfiring and the coil along with the plugs need to be ...
  1. #1
    AQJ is offline Cadillac Owners Member
    Automobile(s): 2001 Deville and 2009 STS
    Join Date
    Mar 2014

    2009 3.6L STS Coil/Spark Plug replacement

    Just received a diagnostic stating that #4 cylinder is misfiring and the coil along with the plugs need to be replaced. Seems like a fairly simple task, but my only issue is that I do not know how to locate the #4 cylinder. I've done an extensive internet search, but was unsuccessful in finding my answer. I also wanted to know if it is always in the best interest of the vehicle to purchase OEM replacement parts, or will purchasing parts from places such as Auto Zone suffice? Any help/guidance in this matter will be greatly appreciated. Thanks.

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  3. #2
    AL REYES is offline Cadillac Owners Member
    Automobile(s): STS
    Join Date
    Mar 2012

    Re: 2009 3.6L STS Coil/Spark Plug replacement

    I have a 2008 3.6 STS found this on internet. 2012-04-07_153657_1[1].gif

  4. #3
    KRSTS Guest

    Re: 2009 3.6L STS Coil/Spark Plug replacement

    Simple task on this engine. I would use only OEM. You can find the coil on the internet for under $50 shipped.

  5. #4
    cdezey is offline Cadillac Owners Fanatic
    Join Date
    Sep 2010
    NY, NY
    I did the same job recently drove much better after replacement, my coil was acting up in #5 cylinder and coil.

  6. #5
    Chinny is offline Cadillac Owners Member
    Automobile(s): 2007 STS4 3.6
    Join Date
    Oct 2013
    Hi, i actually changed my plugs earlier today!
    A few months ago a cylinder completely went out, engine had hard knock, very noticeable something was wrong. Took it to autozone, codes checked, p0300 and p0304 i think. Pretty much cylinder 4 definitely had a misfire and possibly other cylinders. Changed the spark plug on 4, didnt fix it. Changed the plug as well and voila, fixed.

    Fast forward to about a week ago and theres noticeable decrease in performance and loss of power/engine hesitation on hard accelerating and higher rpms. Figured its one of the spark plugs again. Cars at 76,000 miles so i decided to change the plugs(i know, they should last til 100,000). Changed just the plugs today and car runs smooth as butter. The old ones had lots of rust buildup and the gaps were wider than they shouldve been.

    Some more advice, search the forums, a member here has a really handy step by step guide for changing the plugs on a v6, with pictures. I used it and it helped a lot.

    Also, get oem if you can. I ordered all 6 AC delco plugs from rockauto.com, about $30 w shipping and delivery in a couple days. Idk how much coils are but they sell them too.

    Good luck and let us know if you need more help!


    Oh and if you're just changing cylinder 4 you do not need to take off the manifold on top, the plug is accessible without taking it off. You may just need to unhook some tubes. The plug i replaced originally was #4 and it wasnt too hard

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