Wow. I would just tell them to get you another Z. It sounds like the last owner screwed that Z up. Dump it on them and get another. Good luck and stay away from the car wash if you get a new one

Thanks for everyone's input. They are dismantling the dash and removing all the carpet and soundproofing Monday. They will run it through several washes to see what they can find. Last night I had a thought...it has an aftermarket stereo installed by the previous owner. I think that the firewall was drilled through and hit the bundle of wires connected to the ECU. Don't know why I didn't think of it before. And if the hole is in the wrong spot it would get into that passenger side floor board. Anyways, Nissan will confirm with me this week. Either way the dealership that I bought it through said they will make it right. They said they will cover any non warranty repairs or I can take it back to them and they will search their inventory for another car. I purchased this 2011 370Z will 11,500 on the odometer. I am thinking I should demand a 2012 with that kind of mileage. That was one of the reasons I bought the car, low mileage...and the other being I love that 2011 look. What would you demand in my situation??? Thanks Z Community!! I will know for sure what is going to happen by Wednesday.

UPDATE UPDATE UPDATE

Hello everyone,

So I got my car back from the Nissan dealership today. They replaced the carpet and said the problem is fixed. Initially I thought maybe it was a stereo install gone bad, but in fact they said the stereo install was done well. They say that there is an A/C hose on the passenger side floor board that goes through the firewall of the vehicle. There is a grommet that goes around that hose. He said that the car wash undercarriage wash knocked that grommet loose? letting water in the floor board and shorting out electrical components.? They also told me that Nissan does not recommend automatic car washes and in the future to hand wash it. I have several things to think about now that I have it back...should I even chance keeping the car? I will speak to them tomorrow and see if by chance they have another 370z in their inventory. I will update the story as it unfolds. Thanks everyone...

The electrical system would now be my biggest concern. I would return it and find another. Your leak may now be solved but electrical is the biggest headache at this point. To think that your system has shorted out and now its fine? I just can't imagine it being that simple. Somethings bound to show up later down the road whether its a week later or a few years later. Still a higher risk then one that has never had an issue.

Water coming out of the rear hatch is normal when you open it after washing. Mine does the same. But by chance do you a sounds system in the trunk installed by you or by the previous owner? If not sure about the previous owner look in the trunk and look for sub wires. Also could have been wired and previous owner removed wiring so not seeing them doesnt rule that out.

But speaking on first hand experience, since mine was pouring water through the dash like a waterfall, you need to pull the cover off the battery and then the cowling that goes up to the windshield. What can happen is more than likely if a system was wired in, they used the rubber grommet that seals around you main dash harness that goes into the engine bay to run the power wire. If they did like mine, they caused the huge rubber groumet to come loose from clamp that holds it down against the hole. Mine was completely free hanging. Douchbags probablet fought with the groumet and gave up and just closed everything back and didnt tell the owner. Took me like an hour to form that thing around the clamp and wedge it back in like it should be. They did poke the power wire throught the groumet but it sealed fairly well against the new hole that was poked.