I have a 2011 G37x with 117k miles and the Service Engine Soon light came on when driving to work this week. I brought it to my mechanic and he said it showed P0301 Cylinder One Misfire. He also had the following comments:
Removed sparkplug and noted plug was fouled and smelled of coolant. Put borescope in cylinder one when pressure testing the cooling system and could watch a stream of coolant starting to leak down into cylinder one piston. Suspect head gasket failure.

He referred me to the dealership. I spoke with the service writer at the dealership and was told they don't usually see head gaskets get replaced and that it's usually a different issue. Has anyone run into this with their G37X?

 

Don't know but most people aren't taking a car that old to the dealer to get a issue like that looked at out of warranty. So the service guy probably doesn't see that issue there that often.

 

Pretty clear diagnosis... there's only one place the coolant can come from. I don't think you'll get a different answer.

Good luck,


Rick