For my first spark plug change at 64,000 miles and to hopefully correct a misfire, I paid the dealership so that I could avoid the broken spark plug fiasco. It ended up costing around $500, and they ended up twisting 5 of them off. Around 2300 miles later, the #4 cylinder was back to misfiring but was throwing a code this time. As I had just changed the spark plugs, I assumed that it was something else and continued to chase the problem. I have replaced the COP's, paid for dealership diagnostics, checked injectors, etc. Today, I finally pulled the #4 plug. The negative electrode on the Motorcraft SP546 has broken the welds at some point and now resides somewhere other than where it should be. On top of that, the poor plug looks worse than most with more than 10x the mileage. How can Ford still be having issues with their newest plug design for this engine? The third time doesn't appear to be a charm. Here it is next to a new one for comparision. Even afterthe plug change, and no more misfiring, I am only getting around 8.5 mpg with less than 70k on the odometer.

 

See all that black going up stem . Those gases getting by a loose plug act like a cutting torch,even on the intake stroke it sucks oxygen down past the glowing carbon keeping it very hot . . You had blowby . That carbon around the tip gets white hot and glowing ,we have seen this more than a few times . Plugs must be torqued in with a T- wrench 25 to 28 foot pounds . Number 3,4,and 8 are the frequent failures as they are hard to reach . Some guys will bypass the hard to get to plugs ,that's been true for 50 years .
The sp546 should be a good plug ,like anything a very small amount may fail . After the first go round with broken plugs I went with champion 7989 . Their video on the strength of the plug was impressive and has not failed me . I would have faith in the sp546 but too late for me to switch now ,I will keep the 7989 and still use a tiny amount of nickel anti seize on threads and tips . I wince when I see guys using copper anti-seize on alum heads and it doesn't have the heat rating either for the tips.
Ford dropped the need for anti-seize but I just backed down the amount .Ford also went to 60k interval on plugs . Learn to do your own plugs ,nobody will do as good a job as you ,your time is free .

 

Much appreciated, and great info. I am replacing all of the plugs, using nickel anti-sieze, and torquing to 25 ft/lb. I have no issue replacing plugs, but the first time I felt was better served allowing Ford to break the plugs loose and taking any risk. I was wrong and got bitten. Honestly, once I figured out what needs to come off to get to number 4, it isn't that complicated with a couple of extensions and u joints. I also feel better about the sp546 plug with your explanation. With the blow-by, would that have caused any damage to the threads that would prevent it from sealing properly, even with appropriate torque? Also, what are the repercussions for that cylinder after losing the negative electrode to it? Thanks for your help!

 

Alum heads are a great huge heat sink . When studs break off down in heads when removing exhaust the mechanics will weld fill hole to stud and weld nuts on that metal weld fill ,it doesn't harm the threads then they wrench the stud out They use a wire feed welder .You can see it on south main auto youtube . I believe ford tech malukoco also has one . Both sites are very good .
Cross threading alum is the big deal . Also if plugs keep getting loose they can launch the plug /coil and some of the last threads . The pre 04 's did just that they had too few threads . Start your plugs by fingers if cleaned out correctly they should almost finger tighten all the way . It should feel right or restart .I have helped some guys drill out/oversize tap and put inserts in head ,time sert is the best but you have to be very careful . Heli-coils don't last .
When I was a kid there was an old mech that could take an oxy acty torch and melt a broken bolt out of a cast iron block without harming it . He knew his flame and melting temps .
I know what you mean when I had to do orig plugs I followed the ford tsb to the max and further,I soaked plugs for 2 days with carb cleaner still broke 2 . Had lisle tool and it saved me ,I sweated bullets .I said never again .I do clean hole /sparkplug tip area out with carb cleaner as it melts carbon .

 

Lucky for you --- 99 to 1 chance your plug tip is safely lying in the catalytic converter rattling around. Foreign matter like your plug tip - (or ceramic plug tip pieces that aren't cleaned out after using the Lisle tool), will bounce around in the cylinder till they eventually get blown out under the open exhaust valve. The lucky part is - if it happened to get caught under the valve seat on its way out, it can prevent the valve / valve spring from going all the way up and taking all the slack out of the lash adjuster / roller follower!!!! If that happens, a roller follower can get spit out from its normal resting place. They are only held in place by the normal tension between cam lobe, valve spring, an lash adjuster.

 

So . . . "lucky" is ironic in this note?

I hadn't thought of that contingency. Hopefully it didn't happen to Gotdesl or even better, hopefully redfishtd is right about it getting burned off.

 

Had the identical problem with an 07 Lincoln Navigator.... Inspection of the plug indicated the electrode broke off (not burned off as some incorrectly state).
On my plug, one side appeared to have broken off first and the other side looked appeared to have a fresh break (no carbon, clean metal). NGK attributes such breakage to vibration fatigue of the metal. Its my assumption looking at the component that it suffered from thermal fatigue. The plug has only been in the cylinder about a month, and within that timeframe the vehicle was only driven about 2k miles.

Removed one of the other plugs and it had not experienced the same fatigue failure of the metal. The break occurred at the rim of the plug just at past where the electrode was welded to the plug thread frame. It's my assumption that motorcraft has variation in their electrode welding process which causes a fracture to form in the grounding electrode right at the base of the spark plug. Once the spark plug is operated through a few heating cycles, the fracture expands, eventually fracturing completely away from the base. Plug voltage could be moving across the air gap of the broken electrode as the one I removed appeared to be burned on one side (not the other).

These are assumptions at this point. a lab would need to test several of these plugs at random to discover where the failure is actually occurring, however no doubt is a process/design issue. I have seen plug damage similar to this with older engines which would tick over (run on) due to hot carbon deposits on the left on the pistons. (1980s early unleaded petrol days).

I Have not assessed my engine with a bore scope yet, however if there is damage to the piston and valve assemblies, I will be contacting my attorney and filing a civil action under the Warranty rights act. Those experiencing this issue should consider pulling together into a class action, as it clearly appears to be a design or manufacturing issue. The fact that mine occurred with plugs acquired in Mar of 2020, indicates the process issue has yet to be corrected. For the time being, I would suggest using an alternative manufacturers plug.

 

That could add to this problem .A posting on here detailed some of the tail tale differences . One was how the tip was welded on . So just be aware and look them over good . I don't have a link to that posting . The chinese are terrible about counterfeiting as we all know .

 

Yeah, counterfeit crossed my mind, too. The OP said dealership so that ruled that out. But tj hessmon, where exactly did you get your plugs? A month for this to happen is obviously disconcerting.

 

Doubt very seriously its a weld issue.. Most welds of the negative electrode are preformed by robotic welding, which is a highly repetitive process... All of the plugs I had issues with..... the weld was completely intact, where the electrode attached to the case. The destruction of the electrode occurred above the weld point. It was definitely loose plugs (resistance) which caused the destruction. We saw quite a bit of this type destruction when GM shifted to the HEI distributors and wide plug gaps (60-80 thou), back in the 1980s. They later updated the plug gap to 45 thou and the problem went away
I knew what it was when I removed the plugs. All of the damaged plugs were loose... "too much anti seize on the plug threads"

 

I would hope that after that bad misfire you reset the keep alive memory "KAM" so as to reset the fuel tables.