03 ford Windstar engine keeps dying after it squells a little. I be live its the idler pully or P/S pump?

Okay so I have a Windstar that died as I was driving it but it was making a belt squealing type noise I believe it could be either the idler pully or p/s pump. The pump rotates with a little bit of pressure of course then it will get a little stiffer then spin easy again. It keeps dying after a 30 sec to a minute of running and will sequel right before it does so. Any help would be nice thank you.

Briefly run it w/o belt and see what happens as far as the engine running well. Then figure which pulley is hard to turn and you have your problem there.