sdog

I was snowblowing approx 12-14" of snow this am.  Half way through a snow bank, I experienced a sharp loss of power and the engine appeared to be revv'ed continueally.  (Similiar to a chainsaw with the idle set too high).  The throttle switch failed to produce any change in engine speed.  The augers worked fine and the wheels continued to be self propelled, but if any resistance was encountered the engine sounded as if it would stall out.  I was in a snow bank that was pushing over the top, although the speed was set low enough to not make the engine work too hard.  There is no smoke or sign of oil burning.  Any Ideas?