I can start the engine, but it will not stay running in park or neutral. If I put it in drive the engine runs, rpms drop but come back up. Back to park and the engine dies, the low gear up arrow comes on steady, and the indicator on the "w" switch comes on. I have tried running the shift selector back and forth several times and that has not helped. Can you? My local Volvo mechanic can not give me an appointment untill Aug 8. Any suggestions are appreciated.

Well, Nevermind. I have answered my own question. It was not the pnp switch at all. The air hose was disconnected at the point where it attaches to the throttle body. Put that back on and the car runs great. Odd symptoms, though.