I have a 1998 A4 2.8 Quattro with almost 130K on the clock. I need to get an emmisions test to register my car again. I have taken it to be tested once and failed miserably. My hydro carbons were reading 4 times the legal limit in ABQ, NM. I recently replaced my air filter and timing belt. What usually causes these vehicles to fail an emissions test? I wonder could it be the O2 sensor? Or maybe the spark plugs? Any help is very much appreciated.

 

Hydro-carbons could be high do to a faulty ignition system. Spark plugs and wires could cause this.

 

I will change the spark plugs and see if that works, otherwise I will have to see if my ignition is the problem. Thanks for your advice CRAZYHAWK.[sm=smiley20.gif]

 

use good plugs and wires

NGK plugs and oem wires.

also u could tyr some fuel system cleaner, gumout regane

 

Fuel mixture problems cause high CO readings.

 

H.C is pretty much raw fuel or more fuel is been used
I would look at ignition first if everything seems ok
the have a look at wat your O2 are reading....
the pretty much tell the whole picture

 

Have you run a VAGcom and seen what codes are stored?

Could be anything from a bad precat oxygen sensor, fouled or worn plugs, leaky injectors, misfires, bad ignition coils, bad ignition controller, etc