How to lower Hydrocarbons??
 

2001 Deville was at max on HC last time tested 15mph 47/47 25mph 31/31 that was 6 months ago have to have it smogged again for ownership change.. any recommendations on what should i change/check first?? Afraid that it will fail this time..Thanks

hc- is unburnt fuel
first do u feel the car misfiring?
2 reason for high hc ---- spark plug not working well burnt down
fuel injector leaking into engine
i would clean the throttle body which will help air flow, make sure air filter is clean
replace spark plugs check and make sure the wires are not arcing may have to replace them as well
then take vehicle for good drive to burn all crap out after u did the work
what was your readings
hc
co
no

since the car is 10+ years old, in addition to what GMTECHS stated & requested, here are a few insider small things that can also affect the equipment readings to the wrong side, increasing HC.

assuming engine components are running as they should and O2 sensors and Catalytic are both working well ....

a dirty engine .. clean it before the test, cooking the oil deposits on the SMOG test can be picked up by the equipment.

a full tank of fuel can affect the equipment .. make sure the tank is about 1/4 to 1/2 full, no more.

dirty oil emits more byproducts .. get an oil change before the SMOG test.

oil splash .. run the SMOG with oil one quart low, less likely to splash oil onto the super hot surfaces in the cylinders/sleeves creating extra emissions.

A/C .. pull the plug OFF the AC compressor for the test, reducing the engine load.

vacuum lines .. make sure there are NO leaks.

tires .. make sure they are inflated properly or even a little extra.

weather . engines tend to run better and cleaner in warm weather .. if possible, avoid test in cold or rainy weather.

air filter .. these can restrict air flow, remove for the test, make sure you reinstall afterward.

SMOG STATION - run the car on the highway until fully warm, even if they tell you you can turn off the engine, do NOT SHUT THE ENGINE while you wait your turn .. keep it running!


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