The recent crash at London Heathrow AIrport was caused by frozen water in the fuel. It is very difficult to remove the water in fuel. For cars, it accumulates at the bottom of the tank, and then normally get sucked into the fuel injection system and then into the cylinders with the effects described. It is not usually a problem here in the UK, but if there are a lot of filling stations that don't sell much petrol, it can collect in the storage tanks and get transferred to cars. I believe modern fuel filters will hold on to small amounts, hence the need to replace them.

My first Jaguar, a Mark 2, had a glass bowl filter. You could immediately see accumulated water, as it collected at the bottom of the bowl.

 

Yep, I'm a pilot, and part of the pre-flight inspection is to use a little cup to drain fuel from several spots on the airplane and inspect it for water. Water accumulation can be pretty bad on small planes that don't get flown very often. The fuel tanks are vented and as the plane heats up in the sun then cools down at night air gets sucked into the tank. The water in the air condenses on the cool metal parts at night, then drips into the fuel. It doesn't take long for tanks on a small Cessna to accumulate a few teaspoons of water, which is enough to kill the engine in flight.

 

Just an update on my stalling car. After the quick on the road cleaning of the electrical contacts at the TB, I drove the car an additional 700mi and had no additional problem.