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Found a bent spark plug

Discussion in 'SN95 Cobras' started by Tunedprt91, Jun 21, 2013.

  1. Tunedprt91

    Tunedprt91 Well-Known Member Established Member

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    Semi Long Read

    Hey everyone just looking for some insight on what I should do or maybe not do. Heres the story on what has been going on the past few days:

    Sat night: Me and a buddy decided to do a couple of fun runs. Car is running fine all night until I get close to home and do one final pull. It was a 3rd to 4th gear run but when I went to 4th the car started shaking so I let out.

    It didnt die, no smoke of any kind, no overheating but it did have a bad misfire. I was close to home so I just drove it back taking it real easy and when I got home I just parked it for the night.



    Sunday: I checked for any loose connections(electrical) and for any kind leaks(air) and found none. I figured the next step would be to change the plugs. I did drive the car down the street to a autozone to try some coil packs and see if that fixed anything(it didnt). The car did seem to be running a little better but it did have the misfire still.



    Today: I havent touched the car since sunday and today I put in new plugs. All the plugs seemed fine except for the one in cylinder #8 this is what it looked like when I pulled it out

    [​IMG]

    The plugs have been in there for maybe a year so im not even sure that happened sat night during my runs or not. Anywho after I changed all the plugs the car was running perfect! No more misfire and everything was fine it seemed. I drove it to the end of the street and back to make sure everything was cool and it seemed so.

    I cut the car off to go grab the plugs so I can show them to my tuner to see what he thinks. I hop in the car, start it up, and its knocking:fm: Not super loud but its a faint tap tap tap that sounds like it was coming from up top near #8. Now it was NOT doing this when I first started the car after I put the new plugs in.

    I cut the car off and back on and yep its still tap tap tap. So I call my tuner to tell him I was coming by to let them listen to my motor. Before I leave I add some oil to the motor and head out. Its about a 30 minute drive to his shop and when I get there the noise is gone. I let it sit for a bit, start it up, and nothing no noise.

    So now im back home writing to you guys to see what you think. Im going to let the car sit overnight and cold start it in the morn to see if it makes the noise again. I pulled plug #8 again when I got home and it looks brand new still. I havent had the car over 3k rpm since the plug change a little while ago.

    What Im trying to figure out is if my car makes no weird noises in the morn should I just pray that nothing is wrong and continue to run my car as normal? Bent plug and tapping that went away has me worried. Ofcourse if I start the car in the morn and hear the tapping I know im probaly screwed.
     
  2. Tunedprt91

    Tunedprt91 Well-Known Member Established Member

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    Well did a cold start on the car this morn and no knocking or weird noises were heard. Guess ill get a compression test done soon.
     
  3. Dan.J

    Dan.J Member Established Member

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    Strange, GL
     
  4. encasedmetal

    encasedmetal WHINO! Established Member

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    looks like you hit that plug with the piston
     
  5. Noreast

    Noreast Active Member Established Member

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    We're there any chunks missing off the plug ?
     
  6. Tunedprt91

    Tunedprt91 Well-Known Member Established Member

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    Nothing missing off the plug or metal shavings anywhere. Im hoping there isnt a hole in the piston because i believe they did come in contact.
     
  7. Dan.J

    Dan.J Member Established Member

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    Agreed, but why all the sudden? And then new plug and tapping sound that goes away (after it closed the gap again I assume) Confuses me, I would be worried about this one.
     
  8. Dan.J

    Dan.J Member Established Member

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    Personally I would do a compression test and leak down test and try to see the health of that cyl and the rest for that matter. Wonder if you strectched the shit out of rod bolts or rod its self, if so I would think it wouldn't sound good at all though.
     
  9. Tunedprt91

    Tunedprt91 Well-Known Member Established Member

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    Dan the new plug is still fine. I looked down into the cylinder and it looks the same as all the others.

    Im trying to get a compression test setup soon.
     
    Last edited: Jun 22, 2013
  10. blacksheep-1

    blacksheep-1 Active Member Established Member

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    Something..SOMETHING made a lap in that cylinder, every time I've seen a closed plug gap it was because something hit it. It may have magically sucked itself out of an exhaust valve and went on it's merry way, but that's not the type of luck I have.
     
  11. Tunedprt91

    Tunedprt91 Well-Known Member Established Member

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    Ill see if I can get the camera to pick it up but there was a knick on the plug in the form of a small straight line. Almost like someone took a small flat head to it.

    Speaking of being sucked out there was a pop that I heard on the way to the shop yesterday. The thing is I turned the a/c on the moment it happened and just figured it was stuff kicking on so I didnt think much of it. Was like the sound of a big rock that gets thrown under your car.
     
  12. TurboSVT96

    TurboSVT96 New Member Established Member

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    Might want to pull the intake off and check for metal debris. If there is a peice of metal in there it could bounce from cylinder to cylinder. Do a compression check/ leak down test to be on the safe side too.
     
  13. blacksheep-1

    blacksheep-1 Active Member Established Member

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    Probably the exhaust valve being hung open momentarily by the mystery debris. Really the only absolute way to check this is to pull the head and take a look, anything else is an educated guess. You might pull it down and even find it was a waste of time and effort but it's the only way to be sure.
     
  14. stangbanger856

    stangbanger856 Active Member Established Member

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    There is no way the piston hit that spark plug all of a sudden and after you swaped plugs it doesn't do it again. If it was the piston the motor would be toast and you would be abel to tell. From the sounds of it that was some foreign debris that entered the cylinder and after getting squashed between the piston and spark plug it made its exit.

    Please tell us more about your combo? Boosted? N/A? Where is your air filter located? Does the fliter have a hole? Have you recently removed anything from the intake side? Modified IRCMs?

    Pull the upper half of the intake off (shouldn't take any longer then 30 mins) and take a look down to the bottom of the intake to see if anything is still sitting there and check around for damage.
     
    Last edited: Jun 22, 2013
  15. Tunedprt91

    Tunedprt91 Well-Known Member Established Member

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    Here are some pics of the knick in the plug I was talking about

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    Stangbanger the car is boosted. Running a centri and seeing 17lbs with my pulley combo. Motor is built running 8.5:1. The air filter is in the lower part of the front bumper and has no hole. I switched my setup to air/air/blowthru and did mmr imrc delete plates about a month and a half ago but I dont drive the car much.(but I have got on it more than a few times since the swap) Ill pull the upper off and check
     
  16. stangbanger856

    stangbanger856 Active Member Established Member

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    Pull the intake tube off the blower and check the fins on the compressor. Make aure there not chiped or damaged. If they are in good shape the part that caused that was already past the compressor housing. What kind of intercooler?
     
  17. Yellowvenom

    Yellowvenom Member Established Member

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    Is it possible a piece of carbon from the intake track flaked off and was ingested into the cylinder. Closed the plug gap and was then either burnt up and/or blown out the exhaust. +1 on checking the blower, inlet, and discharge tube for damage or missing parts. GL.
     
  18. carfixer

    carfixer Member Established Member

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    You detonated and broke a piece off the piston. That piece closed the gap of the plug. Get a bore scope and look at the piston top.
     
  19. mustanginky

    mustanginky Active Member Established Member

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    this is my guess. mine did the same thing when a ringland went some years back. something hit that plug.
     
  20. encasedmetal

    encasedmetal WHINO! Established Member

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    judging by the buildup on that plug alone you got some serious issues going on
     

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