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year old spark plug gap filled with oil crud

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bross82, Jun 17, 2002.

  1. Bross82

    Bross82 1/2 ton status

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    hey, when i changed out my spark plugs a week ago, i noticed the number 6 cylinder plug had a lot of oil gunk in the gap.... this seems to be the main cause for my truck backfiring when i would let off on the gas in the past month or two.... my question is how bad is the situation really, and is it something that would be expected to cause more problems soon?

    most other plugs looked good... 2 or 3 of the others had some ash residue on it but i dont think it was anything too bad... not even close to the condition of the 6th cylinder plug.

    thanks a lot,
    matt
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Whats your mileage here? You may have some leaky rings. Do a compression test and see what you get. More than likely though I would say you have a bad valve guide or seal. Those are where the stem of the valve comes through your head and to the springs and all that good stuff up top. When one goes bad, then oil leaks down the valve and into the combustion chamber. Is the spark plug shinny or flat? Flat could mean too rich from a bad wire also. But the deposits make me think oil.
     
  3. Bross82

    Bross82 1/2 ton status

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    hey.... as far as the wires i changed them in april, they are ac delcos and should be good... as far as the plug i will have to check, like i said most of the plug had oil gunk all over the metal prong (electrode i think) part and filled in the gap before the lower electrode. it wasnt just oil that dripped on it, it was actually like oil gunk on it. do you mean then just to check the part where the spark was able to jump the gap?

    thanks,
    matt
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    I meant what the plug end as whole looks like. Looking at the coloration of the electrode can tell you whats up. Oil leaking past the valve guide can and will make it do that (shinny and cruded up). Oil is going into the cylinder and being ignited along with the gas, making a nasty and dirty mixture.
     
  5. Sandman

    Sandman 3/4 ton status Author

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    I have the same problem with my number 7 hole. Its the valve guides. I think an umbrella seal should fix it. Right now I am running a hotter plug in it and cleaning it out every few weeks.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    You definitely shouldn't be getting oil in there of course. As was mentioned, I'd probably pull and clean it (not replace, would get expensive) maybe every oil change or so. I pulled one of mine out (OLD motor) and it too was covered in oil/burned oil. Good as new once cleaned, but since the truck smokes on startup and at high RPM, I know that its just worn out. (guide seals and likely rings on that cylinder)

    I (or you) could run a compression test, but if I am gonna work on the heads, why not rebuild the whole thing? : )
     
  7. 70~K5

    70~K5 1/2 ton status

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    When I've had a problem like this and couldn't fix it right away. I save the other 7 good used plugs and rotate them into the bad hole as it fowls that plug. When moneys tight or time is you do what you have too to get by.
     
  8. Bross82

    Bross82 1/2 ton status

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    hey, thanks everyone... I'll try and go look at the old plug's electrode on my lunch break today... and I'll prob clean it every oil change.. I dont quite notice it as much now... but I noticed a huge difference in power the first few days after I put the new plugs in... dont know if it was just mainly due to the new plugs or if a large part was due to replacing that one gunked up plug.

    either way....

    I've noticed before, I have full dual exhaust, the passenger side pipe's exhaust doesnt come out nearly as strong as the driver's side.... even after warming up, cause I was told it may be due to the heat riser, but it did seem stronger after I changed the plugs... but only for a week or so.. i was wondering if it this is mainly due to the plug, or if i'm imagining it getting stronger and its just the heat riser?

    thanks,
    matt
     

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