Blown-Out Spark Plug

A Honda Element got hauled in on a tow truck one night. Big misfire, running horribly when we drove it into the shop. As I plugged in a scanner to read the codes, another tech started pulling the spark plugs, and before I even got the code for misfire in cylinder 2 he already found it.


On the right is a good spark plug, on the left is the one from the bad cylinder. Nobody in the shop had seen this type of failure before. The tip was broken off, the porcelain around the middle was gone, and the whole porcelain part was loose inside the metal outside. We looked in the cylinder with a bore scope and could see some little pieces inside, probably the tip from the spark plug. The threads pulled out of the head when the spark plug removed, which meant the engine needed at least a new head, if not a whole engine because of the bits that could be floating around inside.


These are ignition coils, one connects to the top of each spark plug. You can guess which is from the bad cylinder. Because the insides of the spark plug got loose, heat from the combustion chamber was able to escape and melt the ignition coil.


We went with the whole engine replacement option and got a used one shipped in. Because it was a manual transmission, the easiest way to do the swap was to drop the entire engine and transmission out the bottom of the car on the subframe instead of lifting it out with an engine hoist. It turns out five gallon buckets are strong enough to support the whole assembly.

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4 Responses to Blown-Out Spark Plug

  1. Juan says:

    What was the cause of this? If I may ask.


  2. Juan says:

    Sorry i miss the lose spark plug part, only thing on the car im currently working on (05 Dodge neon sxt) i just finished replacing them a week ago just on Saturday while driving home on the freeway the car just losses all aceleraction and I pull over to the shoulder and seconds later it dies, I let sit for a minute no check engine every thing looks ok, turn it back on and it was a little bit shaky (keep in mind that I have a bad motor mount so it’s been a little shaky) even though it was a tad more then usual so I drove about a quarter of a mile to the next exit. (Always carry my tools with me everywhere I go, except of course on this day since the day before I had been working out in the open trying to finish before the storm set in here in good old salt lake, was able to finish in time just to not finish soaking wet but I just threw my tool in the back of the box truck that we use as a road service) so there I am with nothing but a toothbrush, a pocket knife and the car keys, I unhook the battery and check ever thing from the fuel lines to the vacuum hoses anything that I could get to with my three tool. (Also a week ago I took down the gas tank cleaned it out since the fuel regulator seem to be gettting clogged, went ahead and chang the whole fuel pump assembly, also drop the engine oil and tranny fluid trying me best to manually flush it, changed filter and refilled with full synthetic) anyways long story short could find anything with my limited tool selection (unplugged and check all spark plug wires which are also new) everything looked fine just didn’t sound good at all, also since I had pulled in to maverick I roped the take with premium gasoline (thinking maybe some bad gas) but nothing at all, well finally we got a ride home and had the car towed home on Sunday and today now Monday I turned it on and it sounded like there was in issue with the timing called me dad ask the probability of the timing getting out of sync with out the timing belt being broken or falling off, he asked me did you check the spark plugs and said no, for one on Saturday I didn’t have the tools to check them internally and visual looked ok secondly it would of been one of the first things I would of check if I would of had the more tools maybe also to do with them being but a week old. But anyways took them all off and all four of them burnt like the one in the picture, going back to autozone to get new one and then back to my investigation of the cause in this case.


  3. Pingback: Mechanical Malarkey

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