Where are you slapping the door? I am willing to bet it is your switch. You can remove the switch assembly and open the driver switch. The driver switch has the auto down function and if it is not assembled correctly it won't work right. I suggest you pull the switch assembly out (with the door panel still affixed to the door), disconnect the switch assembly and take it to a place (like a well lit table top) where you can safely disassemble it without losing any of the small parts (there is a spring in it). Re-assemble the switch and reconnect it to the plug and try it.My drivers side power window decides when it wants to work. sometimes its fine, others it only goes down and ii have to slap mydoor for it to roll up. guessing i have to buy a new motor and everything. took off the door but there is a piece of sheet metal blocking my pass to the motor.. anyone know how to fix this in Az? or know how to install and can give me pointers.. I know i come on here a lot asking for help, but so far everyone has been awesome- thanks in advance for the help!
Hopefully the successful re-assembly will fix the problem, if not then you could switch the front passenger switch in the assembly position and see if the problem persists - if it does, then you have a motor problem, if it doesn't persist then you know you need to replace the driver window switch!
Let us know what you find.