What is wrong with my 05 Chevy Cobalt?

I have 2005 Chevy Cobalt, sometimes the car stalls
out really bad & makes a noise I've never heard. It
sounds like goggling oil or something . & it loses
all power & tries to die. When I come to a stop I
have to put it in natural & hold the gas pedal at a
steady past if I don't then it will die. Sometimes it
just randomly dies going down the road. Does
anyone know what the problem could be? I've
cleaned the throttle body. It helped it out a little but
it's still doing it.