HC too high at 15mph smog test, 1992 Nissan Sentra

Distributor rotor, cap, timing chain, spark plugs, spark plug wires, air filter, oil filter, and changed the engine oil; still failed smog test for HC too high, what else could it be? Please advice.

Answer:		First thing is to find out if the high HC problem is related to the ignition system (which you've changed almost all the components to), or the fuel/combustion system. Rich or lean fuel conditions, as well as low cylinder compressions can cause high HC as well. Your smog check Vehicle Inspection Report should show your Sentra's emission scores. Look at the CO emission. If this is either higher or lower than the state's averages, your Nissan's high HC problem could be fuel related. We recommend conducting a compression check first to make sure compression is good on all cylinders, and then move into fuel system testing. posted by SmogTips Support