Apparently, this hose sucks air out of one of the magic components of a carburetor, i.e. the preheater. If this hose slips off the little connector it sits on, the preheater shuts down.

If the air is very humid (on a rainy or foggy day) and the temperature outside is below about 10 degrees centigrade, this failure of the preheater will cause the carburetor to freeze over. Effect: the power of the engine drops slowly but surely, and in the end, even at full throttle, the engine will hardly turn faster than when idling. Finally it will die completely.

The first time, this happened to me when erratically driving through a town, looking for the house where a party was supposed to b. On January 27th, 2001, it happened to me for the second time; both times, it was my mother's old VW Golf II. That second time, it happened to me on an Autobahn intersection! When the car finally rolled to a halt, I was stuck on the acceleration/deceleration lane connecting on-ramp and an off-ramp. I nearly got killed.