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Spark plug help needed, 5.3 Tahoe, it of insulator broken

Discussion in 'General Tundra Discussion' started by Youngfrankenstein, Feb 17, 2020.

  1. Feb 17, 2020 at 1:48 PM
    #1
    Youngfrankenstein

    Youngfrankenstein [OP] New Member

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    Hello, my wife’s 100k Yukon has had a miss. Finally spent $80 on plugs. At first I was like; “crap, these look fine.” Then I found this lil’ turd on cylinder #7.

    car runs much better. My questions as, why did it look like the threads were oily? Was it not firing & un-burnt oil was soaking sown threads?
    Thank you.

    E26225E0-6BFE-42CB-87E9-3FA9957E348E.jpg
     
    Mountun Goat likes this.
  2. Feb 17, 2020 at 2:42 PM
    #2
    ColoradoTJ

    ColoradoTJ Moderator Staff Member

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    I would put the new plug in, run the vehicle, cool it down, pull plug.

    It could be the valve cover o-ring if the oils on the spark plugs threads still happens. This would be the cheapest of what could be wrong.
     
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  3. Feb 17, 2020 at 4:52 PM
    #3
    Nick T

    Nick T New Member

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    The LS engines do not have the valve covers over the spark plugs, they install on the side of the head just like other OHV Detroit V8
    The oil would come from leaking valve seals or sticking rings, the broken porcelain is probably from engine knock.
    Lots of residue on the plugs and no maintenance history mentioned in the thread, so I would suggest a compression and leakdown test.. you may also want to run a fuel injection cleaner thru it or higher octane fuel to stop the knock.

    Luck
     
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  4. Feb 17, 2020 at 6:23 PM
    #4
    ColoradoTJ

    ColoradoTJ Moderator Staff Member

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    Damn. I was thinking Toyota and read LS. Good answer @Nick T


    Even more troubling, I have an LS 5.3 on a crate in my garage. Lol
     
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  5. Feb 17, 2020 at 6:27 PM
    #5
    Mountun Goat

    Mountun Goat It’s grazing season

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  6. Feb 17, 2020 at 6:58 PM
    #6
    Youngfrankenstein

    Youngfrankenstein [OP] New Member

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    Thanx so much for all the info. Much appreciated. I will pop it out this weekend & take a gander. I got mi fingers crossed. Been doing 87 octane by the way.
     
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  7. Mar 7, 2020 at 11:37 AM
    #7
    Youngfrankenstein

    Youngfrankenstein [OP] New Member

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    FARTS!!!!!!!!!!!! Just checked the same cylinder. Car hardly gets any mileage, wife works .5 miles from home, but does to in town errands. This is not what I wanted to see.

    IMG_0541.jpg
    IMG_0542.jpg
     
  8. Mar 7, 2020 at 11:38 AM
    #8
    Youngfrankenstein

    Youngfrankenstein [OP] New Member

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    What the Crap!?!?!? Valve seals? I REALLY hope it is not rings or anything. Lil' over 100k. Any other ideas?

    I know it isn't a Tundra, but this is the only auto forum I really hit.

    Thank you for any tips!!
     
  9. Mar 7, 2020 at 11:40 AM
    #9
    Youngfrankenstein

    Youngfrankenstein [OP] New Member

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    FYI, 100k of easy throttling around town, she never floors it and it has never towed.
    Thank you.
     
  10. Mar 7, 2020 at 11:55 AM
    #10
    Nick T

    Nick T New Member

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    I would start with replacing the coil on that spark plug.
    Disable AFM if you have it.
    If the new coil and disabling AFM does not help, then you have a leaking valve stem seal... there are ways of replacing the seal without removing the head, but it is still a big job... depending on if the oil residue goes down with a new coil, you might be able to get away with just using a hotter plug.

    Regards
     
  11. Mar 7, 2020 at 12:03 PM
    #11
    landphil

    landphil I can’t be serious.

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    Time for a leak-down test and even a scope of that cylinder before throwing more parts and labour at it. There’s a pretty good chance that cylinder is scored up from the broken porcelain isolator, in which case replacing any coils, valve seals... are a waste of good money.

    Now there’s a chance that’s not the case, and an outcome we’d all prefer.
     
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  12. Mar 7, 2020 at 12:10 PM
    #12
    bleach

    bleach MEME Fiend

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    Either it has a bad stem seal or it's not getting warmed up enough or both. It's easy to fix. You don't need to pull the head for it. Pull the valve cover, remove the spark plug, bring the cylinder to TDC and pressurize the cylinder with a spark plug adapter from an air compressor. You can buy a lever type valve spring tool at most auto parts stores. I've done this on SBC and other engines. Easy.
     
  13. Mar 7, 2020 at 12:32 PM
    #13
    JohnLakeman

    JohnLakeman Burning Internet Daylight

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    Yep, now THAT'S what I'm talking about. Very good chance that porcelain bit and your cylinder have been fighting to see who's toughest. That cylinder is now barely firing. Scope and leakdown test before anything. :(
     
    Last edited: Mar 7, 2020
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  14. Mar 7, 2020 at 6:52 PM
    #14
    Youngfrankenstein

    Youngfrankenstein [OP] New Member

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    Been out doing work crap all day. I did read up on AFM and how the #7 lifter is known for failing.

    I need to reread all these posts and start searching the web.

    Thank you so much guys for your support. I kind of want the car to go away if it needs mucho work.
     
  15. Mar 8, 2020 at 5:32 AM
    #15
    bleach

    bleach MEME Fiend

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    It really shouldn't need a lot of work at 100K unless it was neglected. I'm not completely familiar with the 5.3 but I think they should go to at least 200K without too much work.
     

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