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Misfire Diagnosis and Spark Plug

 
Old 01-23-2017, 04:09 PM
  #11  
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Default RE: Misfire Diagnosis and Spark Plug

First time I addressed the carbon buildup in the hole beyond the threads I used a set of steel/brass/stainless bristle thread brushes from Harbor Freight. I had a serious bunch of buildup - broke off 6 of 8 spark plugs. I set each piston at top dead center in turn (To keep from having the problem this poor fellow had - http://www.ford-trucks.com/forums/13...lp-piease.html The carbon dust and most other junk will blow out of the exhaust valve as soon as it starts - but I only rotated the bottle brush one direction - thinking that would lessen the chance of steel bristles coming off and going inside.


On subsequent plug changes - I have crimped a piece of rag on a length of coat hanger and put it in the chuck of my battery powered drill. With enough treatments of Carb Cleaner on the rag, that would probably do the job on the worst case of carbon.


If you choose to use anti-seize - the recommendation is only apply sparingly to the plug barrel - not the threads. @redfishtd correctly states my disagreement with it. The 'metallic' compound, like the carbon buildup touching the long extended snout on the plug conducts heat AWAY from the plug tip effecting the designed (high heat range operation) - aggravating the misfire problem that so many have, even after plug change and new COPs. ALSO, Partly because I believe the carbon around the snout - if it was tight enough to twist the nose off the old plug - I believe it is enough to 'fracture' new plugs going back into the same carboned up hole.

Last edited by F150Torqued; 01-23-2017 at 04:18 PM. Reason: Add title & mispellings
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Old 01-24-2017, 11:04 AM
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Thanks so much F150Torqued for expanding on that. I like your input and @redfishtd about the anti-seize not being put on the plugs, even just a small amount, because it changes the heat range. Especially if I have carbon buildup already there it will only worsen the heat range issue that may be present. When I picked up my new MC spark plug at the dealer today I asked the service desk person, which isn't a mechanic but still had input, on whether hey normally use anti-seize when putting in new plugs and he said "no."

Because I'm worried about the issues you raised with cleaning out the plug well and the dangers of hydro locking my engine with carb cleaner, I may take it to a shop and have them do a full service carbon deposit clean test to remove from injectors and all. My vehicle is 110k miles, 12 yrs old and I don't think I've ever had it serviced to remove carbon deposit buildup. In the last few months I moved and now only drive about 9 min to work and in December we had many weeks of temps at single digits or teens. Not driving long enough to allow the plugs to get hot enough to burn off carbon is probably what happened. You think this is a better solution for my situation?

Also, since I won't be using anti-seize, should I still torque to 25 ft-lbs when putting in he new one? I've read on other forums and online that 13-14 ft-lbs is recommended, but then saw from others that this is too low because the plugs may have a tendency to come loose or blow out of the cylinder head. I will hand tighten first to make sure it doesn't get cross threaded, but just want to confirm the torque I should use without anti-seize. Thanks!
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Old 01-24-2017, 02:48 PM
  #13  
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I do not believe the possibility of getting enough chemical in a cylinder to hydro lock it with a soaked piece of rag no larger than you could cram in the lower part of the spark plug hole, is a concern. I'll bet the piece I crimped on a coat hanger wire was no bigger than 1 1/2" by 3". I have to re-soak it several times and run it in /out of there with my drill to get it to come back clean - but bet no more than a few drops get on the piston. Blow air down in there. That'll dry it out. I'm sure you can do it just fine.


Your 9 min drive to work 'highlights' the design purpose of that long snout on the SP515 - without it contacting the inside of the head. By the time the cylinder fires 50 times, that damn plug snout would be 500 degrees - if NOTHING is touching it.


The factory service manual says 25 ft-lbs (and they weren't thinking anti-seize. Hand starting, yes ^^! They should screw all the way to the seat by hand.


To me, it sounds like you're doing everything right. Just make sure everything is super clean, stretch the spring and clean contact areas, use the dielectric grease and use a good pliable (or new) boot.


Best wishes

Last edited by F150Torqued; 01-24-2017 at 02:50 PM.
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Old 01-25-2017, 04:26 PM
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I use brake cleaner and fill the plug well with the plug still in and let it sit for a while and then use air to blow out the well and then remove the plug. A bottle brush could be used while the brake cleaner is in the well soaking. Be sure to wear safety glasses and keep your mouth closed when blowing out the plug hole!
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Old 01-25-2017, 05:33 PM
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Good points for all that foreign crap that can collect around the spark plug, @JollyGreen48. I should point out that we are also talking about cleaning carbon out of that deep hole 'beyond' the threads. Carbon build up in there is what builds up around the long snout on the SP515 where it extends way down into the combustion chamber. It's detrimental effect is two fold. It allows heat to conduct away from the electrode into the head, and is responsible for binding on the barrel - potentially cracking new plugs / or twisting off the barrel on subsequent plug removal.
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