HC (Hydrocarbon) is raw fuel otherwise known as gasoline. The typical reason your Ford Taurus could have failed for high HC would be defective spark delivery however your Ford's fuel system has a lot to do with how much HC is left in the exhaust after combustion also. A "rich" or "lean" fuel mixture would contribute to high HC as well.
We recommend first inspecting your Ford Taurus's ignition system, spark plugs, wires, distributor, ignition timing, and if everything looks ok, move on to the inspection of the fuel delivery system, ie oxygen sensor (s), engine coolant temperature sensor, mass air flow sensor. Inspecting these components will require some auto emissions know-how and proper inspection tools.
The link below will give you a full list of problems which could cause high HC smog check failures.
What Causes High HC?
