So I just notice that white tank(green circle) is empty what is it for and what goes in it? I'm pretty sure is not just there for looks

Also today when I was coming out of the driveway in reverse the car just shut off(maybe I stall it like a noob, dunno). Anyway after that happen it wouldn't star. The engine made noises like if it was about to start another thing that happen with this was the radio wouldn't turn on either, but all the other electrical stuff did.


TY for the help~

 

Are you referring to the tank at the firewall on the passenger side of the engine bay? If so, then yes, it is there for looks. Remove it, and cap off the nipple to which the hose connects on teh manifold. This tank is for the sub-zero start assist system and Mazda issued a TSB for all dealers to remove it.

As for your other problem, when is the last time the car had a full tuneup?

 

http://img300.imageshack.us/i/zcvsez.jpg/
Yes that tank sorry image attachment never works for me.

The car haven't had a tune up for more than 3 months as far as I know.
What I gotta do for a tuneup besides changing oil, oil filter, air filter?

 

Sounds flooded, maybe signs of a rebuild in your near future, depending on how many miles of course and your ACTUAL compression numbers.