Spark plug ceramic broke off - Piston Damage?


Mar 13, 2019
Fort Myers
As the title suggests, I encountered a Broken piston ceramic sheath/shield as shown below.


initially encountered misfires on cyl 4 on WOT however Car ran fine if I didn't go into boost.

Checked all wiring coils and plugs on cycl4 and low and behold about half of the ceramic sheath was missing. (Explains the arching/misfiring.)
-Purchased a Borescope to asses any damage and took these photos. valves looked perfect however can't say the same for the piston.
I'm not experienced to know if this is catastrophic.
-I am not sure But can imagine that it is resiude/damage from the ceramic.. I would also think that the ceramic would have gotten obliterated but much is left to be addressed here. I'm wondering if this will go away or if the piston is totally F'd. I'm going to do a compression test in the mean-time however any advice/insight would put me at ease. Thanks in advance.




Nov 22, 2018
Looks like carbon buildup. I wouldnt be too worried about that. More worried about the valve but since you have good compression, I say you dodged a bullet.
Just keep motoring on :)


Apr 19, 2017
The carbon pattern is totally normal. You need to get a small hose connected to a strong vacuum cleaner and try to vacuum the shit out of the affected piston. Just to be safe. I predict that the ceramic parts have long been ejected out of the engine through the exhaust valve...there is literally nowhere that particles can go except for OUT through the valve.


Jul 27, 2017
I don't know how the piston or cylinder couldn't be severely damaged but the compression test seems to suggest other wise.

There are alot of fake NGK plugs circulating. Suspect you got one because they seem to be prone to the ceramic breaking.
Wouldn't dare use Chinese spark plugs in my car. The problem is knowing which are real and which are fake.

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