I have a 1990 240sx and the passenger side window is all messed up. It will roll down, but too much pressure and it will just fall down. And it doesn't roll up at all, but the motor still turns in the door. What could the problem be that is causing this to happen?

there is a track that the window sits in, this has either clips or a grove made of plastic. the clip could be broken, pull out your interior panel and check.

maybe it isn't screwed into the assembly...remove the door panel and look to see if it is mounted to the motor assembly.

a simple inspection might help. remove the trim around the window (for more info, download the service manual on vsiev's signature) and see if you can find out the problem yourself.