2005 V6 Honda Accord exploded spark plug

I have a 2005 V6 Honda Accord with 76K miles on it. I purchased this car new and have had this car religiously dealer maintained. A few weeks ago the spark plug in the #5 cylinder worked its way loose out of the head and exploded sending metal into my engine. The service manual states that these plugs are to be changed at 100k. Have you seen this issue before?

I was able to get Honda Americas to pay for half of the repair as a good will - for which I was grateful- it still cost me $2911. When I called to get clarification and stated that this looked to be a flaw in their assembly process (i.e. torque the plugs to some spec), I was told that if I was unhappy that their portion of the covered amount may be rescinded. Pretty unfair in my opinion as I think that all of the cost should have been covered.

I would say that ½ price from the dealer was a good deal, assuming the warranty was out.

That 100,000 miles is the recommended time to replace all the plugs. By that time they are usually starting to wear. The problem you had was not the usual one, but a failure of the plug or engine. It is not likely anything you did or did not do nor anything the dealer did not did not do. I suspect the new car warranty was no longer in effect, so the dealer was really doing you a favor.

If you’re absolutely certain the spark plugs in that engine have never been out before for whatever reason this would mean that the plug was overtightened when the engine was built or the threads were not cut properly, also during the engine assembly.

As to the cost I think you were flat out gouged. For that kind of money I assume they replaced a cylinder head? If so, this is not necessary.
There are various thread repair kits out there that have been used for many decades to repair problems like this. A hundred or so dollars should be the max.

As to good will, Honda paying half, etc. that is also a bit of smoke and mirrors. That half price that you paid more than covers any warranty labor and parts used.

Although I suppose it wouldn’t be completely unheard of, but I have seen this happen a number of times but have never seen “metal sent into the engine”. Usually, everything gets sent out through the spark plug hole, leaving everything but the spark plug hole and coil pack (for COP engines) undamaged. How did they determine that the entire engine was destroyed by this event (that WOULD be unheard of)? I am assuming that for $6k (total assumed since you paid half), they replaced the engine with a new or rebuilt unit. For future reference, if something like this ever happens again, do not take the car to the dealership to repair this. It seems that they invariably think that this warrants replacing the cylinder head at a minimum and prefer to replace the entire engine over something silly like this. Any decent independent shop with skilled mechanics can typically repair the threads without disassembling the engine for a couple hundred dollars, tops.

Close to $6k for a blown out spark plug?!? You could get a used engine installed for that much money. Reworked head should be 1/2 that amount. I wonder if you actually did pay the full amount and they paid nothing by inflating the bill. Can you describe what the repair order says was done?