Hey everyone. My 2013 sedan just starting leaking water on the driver side floor board after it rained. I haven't had it fixed yet but plan on doing it soon. I googled all over the place and found some good info on another Infiniti forum. It's from G45driver.com and I hope it helps you out. Hell I hope it solves my problem to.
'I can't believe Infiniti hasn't fixed this issue. It's been going on since the G 35's
Here's the link.
G35-G37 Water leaks - probable cause and solution - G35Driver

 

Check your grommet on the firewall if you have any type of added wiring for aftermarket accessories. Chances are the installer didn't properly seal it back up, or your sunroof drain is clogged.

 

Thanks....

 

agree with above, i once made a small hhole in my firewall to run some wires inside and started getting water inside, i just put a bunch of sillicone to cover that hole and problem solved

 

I notice my leak when I switched for summer mats to my rubber winter mats I think it might be my harness so I used some tape around it and leave a rag to help collect some of the water where the brake booster is

 

Agree with all the above, plus, if you've had the windshield replaced, it could need resealing - had that happen on my old Maxima a couple of years after I had it replaced and had water on the floorboard.

 

you can try putting a fog machine in your car and seeing where the smoke comes out, probably a bad weather seal.