High HC is the by-product of a misfire. Your Honda Civic could be misfiring and subsequently producing high HC. A misfire can be caused by rich fuel, lean fuel, and/or a defective ignition system.
Since you've already had a mechanic inspect and repair your Honda's ignition system, we'd recommend hiring a smog check repair certified mechanic to inspect your Honda's emissions sensors and fuel control management system. The emission sensors which should be tested include the oxygen sensors, engine coolant temperature sensor, mass air flow sensor, and throttle position sensor, as well as the engine control computer.
Look over the CO results on your Honda's Smog Check VIR report. If CO appears too low or too high (even though it didn't fail for high CO) your Honda Civic is probably suffering a air/fuel mixture problem.
A smog check repair shop usually will take 2 hours to diagnose smog check failure, at the hourly rate of $65-$85. You will then be presented with an estimated cost for repairs.
More info on what caused high HC
