power window problem

[Low87]

I've got a gremlin in my passenger side power window. Sometimes it works, sometimes it doesn't. Sometimes I can roll it up using the driver's side switch, sometimes only the pass. side switch will do it. When it does roll up, it goes fast and smooth. I haven't been able to roll it up for the last few weeks. The driver's side switch does nothing, but if I hold the pass. side switch down long enough it kills the engine! What do I need to check to fix this? All the wiring in the door appears to be okay.