enter image description here first I replaced a motor mount on my 2001 Honda Odyssey and then a few weeks later that plug was like that but I did not blow it all the way out of the cylinder it was still partially threaded in which an end result I had to Helo coil the head And I solve that issue but I’m still like to know what would cause a spark plug to do that then a few weeks later I’m coming down the highway and getting off an exit and take the vehicle just dies lost power and could not get it started after that try to have a jumped it wouldn’t start when I had the starter tested they said the starter was bad I replaced the starter still no starting I need help

  • Welcome to Motor Vehicle Maintenance & Repair! That is just about the most ugly plug I've EVER seen. As far as the engine running (or not), are you getting any action out of the engine? I mean, does it feel like it wants to fire, or is it just spinning without anything happening? What have you done to diagnose? Is there spark/fuel? – Pᴀᴜʟsᴛᴇʀ2 Apr 2 '19 at 10:30

I've never seen anything quite that bad, even on Ford "Trident" modular V engines that were notorious for such things.

Either the plug was or became loose, and many miles of combustion eroded away a groove that later allowed hot gas/exhaust to melt the boot.

The fact it's down one channel suggests the threaded part of the plug may have developed or had a crack in the threads, which eventually provided an erosion path which digested the plug. Another possibility is a crack in the center electrode insulator, which caused the arc to jump midway from the ceramic to the steel side of the thread. The arc would find the shortest path to ground. Since the arc would be jumping to steel and not platinum, it would erode quickly. If you can clean the center electrode insulator carefully, you may be able to discover this crack.

Pure speculation, as that plug does not look like it would fire at all - which means there would be no hot combustion products along with a host of rough running, fuel consumption, and check engine light problems.

Make certain the vehicle has the right plugs. The wrong brand and/or heat range may have contributed to the issue. That Honda will most likely have come with platinum or Iridium plugs made by NGK as the OEM fitment. Denso and Bosch would work as well, but I would be very hesitant to throw in cheap 99 cent Autolites. Modern Asian OEMs use small electrode platinum plugs as a mandate. What parts store claim "fits", may cause a bunch of problems later. It's painful, because the factory Iridium plugs might cost 14-16 bucks each.

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  • Plug was loose for sure. – Moab Apr 6 '19 at 0:50
  • @Moab hard to tell, but the center electrode appears to be gone. I'm leaning more towards the spark leaping of the threaded steel bore, and carrying metal away on every spark. In any case, pretty ugly. Might have even caused a fire. – SteveRacer Apr 6 '19 at 1:33
  • Nah, it was loose and hot combustion gases escaping up the very loose threads did the damage, not electricity. – Moab Apr 6 '19 at 1:43
  • @Moab You're probably right, but I'm surprised it's up one channel and not uniformly melted around the threads. Back to a possible vertical crack in the threaded portion from the start. After all, the plug itself is always exposed to hot combustion gasses, so why don't they all melt? I suppose if it was loose the heat transfer away from the plug may have been compromised. – SteveRacer Apr 6 '19 at 1:55
  • Hot gases are much hotter when concentrated and moving through a high pressure leak, its like a blow torch. – Moab Apr 6 '19 at 6:07

i have seen this happen on A track where nitro is being used . absolutly can melt the plug body from intense firing . also can damage the engine .. other than what i suggest the plug may have been faulty and just melted . either way the plug melted and has caused deeper engine probably piston big end damage.

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