HI MY NAME IS JOHN I HAVE A 1991 CADILLAC SEDAN DEVILLE I JUST PURCHASED IT IS NOT A TOURING MODEL HAS NO E CODES IN THE SYSTEM NO SERVICE ENGINE LIGHTS BUT FAILED SMOG TEST AT 323 IDLE SPEED HYDROCARBONS WHEN MAX ALLOWABLE IS 220 I READ SOME INFO SAID IT COUND BE A LOT OF THINGS I WAS WONDERING A LIL DIRECTION WOULD BE HELPFUL AS I JUST DO NOT WANT TO START REPLACING ITEMS UNTIL I FIND IT THANX JOHN HAS 135,000 MILES IDLES ROUGH A BIT

 

Verify first that engine is running up to normal temperature. If running too cool, below 195 to 210 degrees, you can get this reading. I've also gotten past this reading by using one gallon of denatured alcohol to a half tank of fuel. Alcohol provides more oxygen to lower this reading.