1988 Ford Thunderbird failed smog inspection due to high HC.

Hydrocarbon (HC) is basically raw fuel. The number one cause of high HC is defective ignition system. We'd recommend starting with having a smog check repair station inspect your Ford Thunderbird's ignition system. During the combustion process any number of engine conditions can cause emissions failures. Out of the three systems your engine relies on to produce combustion (air intake, fuel delivery, and spark control), the spark system has the components which require replacement most often. Sparkplugs and spark wires are constantly exposed to high temperatures and high voltages. You must ensure your engine's ignition system is functioning properly, by inspecting all the sparkplugs and their wires. If any of the plugs look worn out or have excessive carbon build-up replace them immediately. The distributor cap should also be inspected for cracks or excessive carbon deposits. If it appears that the cap may be faulty, you will need to replace it. More then likely you will see an instant performance increase once these corrections are made. Once you ensure the ignition system is ok, you'll want to move on to the fuel delivery system. A smog check repair station will first have to find out if your vehicle's fuel feedback system is working properly. This includes ensuring the oxygen sensor is working properly, your Ford's emissions computer is receiving the signals from the oxygen sensor, the computer is computing the data properly and sending the correct signals to the fuel injectors to either increase or decrease fuel delivery to the combustion chambers. Too much fuel in the chambers will cause a "rich misfire", producing high HC. Not enough fuel in the combustion chambers will cause a "lean misfire".