1994 Dodge Stealth Emission Failure - High HC & High NO

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1994 Dodge Stealth 6 cyl Front Wheel Drive Automatic 117000 miles

I live in Phoenix, AZ and failed an emissions test for my '94 Dodge Stealth. I have owned this car since it was brand new and it's never failed before. Phoenix tests 3 categories (Hydrocarbons, carbon monoxide & oxides in Nitrogen).
My Hydrocarbons were 0.85 (grams/mile) and the application standard is 0.80 (Failed).
My CO was 4.71 and application standard is 12.00 (It passed this test)
My NOX was 3.29 and the application standard is 2.00 (Failed).

The car runs good and gets great gas mileage. Gas mileage has remained the same since the car was new. I have not done any modifications to the airfilter or exhaust and I changed the plugs about 4 months ago and also switched over to a fully synthetic oil the last time I changed the oil. One thing I did do, was remove the thermostat during this past summer. I did this because the summer's in Phoenix are brutal, sometimes reaching temps above 115', with triple digit temps most of the summer. After going through 2 thermostats in a year due to them "sticking" (usually shut), I decided to remove it completely to let the coolant flow unrestricted. Each time I changed the thermostat, including this last time when I removed it completely, I flushed all of the coolant out really well, including the radiator.

Any ideas on what I can do to lower the HC and NOX?


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have the same problem?
Wednesday, February 6th, 2008 AT 9:06 PM

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