2012 G37x. Replaced Battery after having to jump the car when it died when an iphone was plugged in and charging. One week later it began to run poorly. Low idle, shaking while in gear, service auto light on. Took to dealership and told cylinder misfire due to bad spark plug. Replaced all and it ran for 4 days then died while driving. Battery power to all systems but would not turn over only cranks. Back to dealership and told a cam position sensor. Replaced only the driver side sensor and told it would still not start. Also told it was low on oil and the engine is probably damaged. Transferred to personal mechanic who says engine is fine, but car will only start with cam sensor removed. Also he reports new problem with transmission shifting "hard". proposing removing the engine cover to check the cam flywheel and shaft position. Seems like a sensor problem to me any help appreciated.

 

A lot of those symptoms sound exactly like my father in law had with his Kia Optima turbo. Dealer was looking at everything and it ended up being the alternator. Worth looking into.

 

I thought alternator right from the beginning with all that electrical talk. It's an easy test to check it. Autozone and many like them test them for free. Shouldn't be going out this soon though. How many miles on it?

 

No codes with all those problems?

 

I thought the same with my father in laws car. And his is a 2015 with under 60,000kms (canada). And it was his alternator.

 

nslamon - I'm having the same problem with our 2013 g37. Only 52k miles. Dealer said engine sludge, new engine, $6k - and Warranty won't cover it.
Did your mechanic figure anything out and give you any options ?? Thanks.