|
Hydrocarbons (HC) are essentially fuel which was not burned during the combustion process, main sources of incomplete combustion are rich air/fuel mixtures, low engine temperature and improper spark timing.
And, an increase in the Carbon Monoxide (CO) emission is normally accompanied by the increase of hydrocarbon (HC) emission because of the lack of air to completely burn all fuel mixture.
Yea, a full tune-up is recommended (if you hadn't done so)... doing this will narrow down all the possibilities when you actually fail the emission test.
I'd also agree with new cat, universal cat will do just fine (got one from a local muffler shop) goodluck!
__________________
294K+ miles; original power/drive trains 
|