Toyota Repair: Emissions Failed - Check engine light off, fuel hydrocarbons, hc emissions

Question
Hello,

I have a 93 Corolla LE (1.8L).  My car failed the emission test.  HC read 434 and CO% was 1.96%.  Check engine light is off.  I checked the wires, spark plugs, and spark plug wires.  They all look ok.  What could be the problem?  

Thanks

Answer
High HC emissions are always caused by excess unburned fuel(hydrocarbons) this is usually caused by incomplete combustion, this happens either because there may be an intake air leak or an engine misfire,first check for a possible intake air or vacuum leak then I would recommend doing a compression test of the engine to see that there is not a leaking valve or other loss of compression. If the compression turns out to be ok then I would recommend replacing the distributor cap,rotor and the spark plug wires.