ALFAGTV6.COM

HEELP!my gtv6 82' is giving me a very high hc reading.i've put in a new O2 sensor and it is a 4 wire and have tried propane outside all connections to the intake after the afm.as very high HC is caused by lean fuel if there was false air coming in the rpm should rise if a intake air leak existed.no dice.no increase in rpm.any ideas would be greatly appreciated.

High HC could be from an overly lean or rich mixture. It needs to be close to 14.7:1 to get the HC numbers down.

Did you check your mixture? I think a good sideband AF gauge would serve you well, if not it's always a guess.

If you found no un-metered air going into the intake, that means the mixture is more than likely rich, not lean.

Make sure your plugs are all good (plug condition, gapped), oil is changed.

Actually using 87 octane gas would be good, since I believe it burns quicker as it has less knock resistance. So it's bad for performance and will ping under load, but may be good for smog testing as there is less chance of unburnt gas going out of the combustion chamber.

BTW my friend went to dyno his 24V Milano (very high miles) in San Jose, and it was cleaner than his low miles E46 M3. All it has is a stock 164L cat.

HC is caused by lean fuel

High emission of Hydro Carbons is the result of unburt fuel not being fully consumed during the combustion process. So the suggestion that it is a result of lean fuel is completely wrong.

More likely it is the result of insufficient air but more likely too much fuel.

Did you recently service the car? If not, do a complete filter change (air, oil and fuel), oil and plugs.
Usually helps a lot, especially if your valve seals are worn.