Unburn Fuel

[lincolntran]

i just learned that my failure of emission was caused by UNBURN FUEL. Can some one help tell me what's the cause of unburn fuel ?

thanks

[SRK]

Normally a misfire. Bad plugs, wires, cap, that sort of thing. CO is bad combustion, rich, but HC is fuel not burned at all.

[wwest]

add leaking injector(s) to the list.

[bartkat]

Unburned fuel, (raw gas) should show up as black smoke out the tailpipe.

[SKperformance]

ifit is unbrunt it depends how high

it is probably a bad cat since it is the clean up for all extras that a bad oil burning engine car even pass emissions tests with a good cat ,belive me i know .

A motorvac can help considerable but unless an injector is leaking badly or a non firing cylinder then it is the cat.

[92Lex]

If CO goes up usually HC will also be elevated. If your HC is high because of a misfire your CO should be low because in order to have CO you must have spark. So high CO and HC together is usually from a rich running condition like SRK said. You had BOTH of your catalytic converters replaced right?

[lincolntran]

yes, I replaced both cat.

Here is my last emission test result:

http://www.htatlanta.org/images/lastEmission.gif

thanks

[92Lex]

Is a certified test and repair station doing the repairs/diagnosis on your car? Can you list exactly what has been serviced on your car ever since you owned it? Did you just tell the technician to replace your spark plugs and catalytic converter(s) or did you actually let the technician diagnose the problem?

The reason your old catalytic converters failed is because of overheating due to your excessively rich running conditions. If you don't find the culprit of why your vehicle is running rich, your catalytic converters will go bad again.

I think it might be your Mass Air Flow sensor...there's many reasons why your vehicle will run rich...so don't hold me or anyone else to this because it's actually almost impossible to tell you exactly where to look.

You definitely have a rich condition (too much fuel and not enough air).

It could be anything though....high fuel pressure, leaking fuel injectors, clogged air filter, fuel saturated oil, MAF sensor, ruptured fuel pump diaphragm, unproper routing of vacuum hoses, circuits shorting to ground, vacuum switches malfuntioning, ignition system malfunction....you get the point. You should definitely have the ignition system checked out first because of the high HC failure.

Take your car to a test AND repair station and let them do the diagnostics...they'll guaranty that your car will pass the emissions test after repairs.