Programbo

Hello. Long story short my brothers 1994 Dodge Caravan with a 3.0L automatic failed the Maryland Emissions test today because of to high a reading in the HC Hydro-Carbons area. It wasn't outrageously high just 227ppm instead of the 175ppm limit. It was fine in the others areas (CO2, Catalytic etc) It has no trouble codes showing so what area should I look into which might be producing a high HC output? Thanks

jnicewan

HC is basically raw fuel, so finding raw fuel in the exhaust is usually an indication of improper combustion (not always though) If the engine seems to run ok and not worn out or low on compression, you probably need to check the basic tune up items (plugs, wires, cap, rotor) Run a bottle of good injector cleaner through the fuel, maybe one can of seafoam in the tank, and one can flushed through the throttle body/intake.

Your HC level is not too high so you might be able to clean it up with the above tips, unless you have already done that. An aging catalytic convertor might be the problem too. It is normal for an engine to not completely burn fuel, thats one of the functions of the catalytic convertor-to clean up the exhaust.

Mr Talon

HC is partially burned fuel, CO is raw fuel.