What's the purpose of this fuse?!?
 

Just out of curiousity, when you open the hood and check the fuse box by the battery, there's a Fuse that says " Eng cont"

What does that do? The mechanics at the dealerships couldn't even tell me what it does hah and I would like to know what the fuse does.

That's the Engine Control fuse. From what I've read here ~~> http://forums.maxima.org/showthread.php?t=525507 it has to do with the o2 sensors.