My car is failing the Carbon Monoxide Loading portion on the State Emissions test.

Asked by May 11, 2009 at 04:10 PM about the 1969 Chevrolet Nova

Question type: Maintenance & Repair

My '69 Nova has about 60,000 on it's 350 V8. It has an Edelbrock 600CFM carb, which passes really low on the Carbon Monoxide idle test. I don't understand how one test could be very low and the other be very high.

My inclination is to go back to work on the carburetor. But perhaps the timing needs to be retarded a few degrees? Just a point in the right direction would help me. This is a California car that I'm trying to get to pass Arizona Emissions. Thanks.

By the way- already tried the parts store "Guaranteed emissions pass" pour in the gas tank solution and higher octane fuel. Put a new K&N air filter on it and checked the plugs. They look clean. The oil was recently changed as well

4 Answers


If you don't have a catalytic converter, put one on. If you have an old 2-way cat on put a newer 3-way cat on. I know it sucks but it'll make an immense difference in your emissions.


damn, i don't know what to tell you. I'm afraid you'll need to install a catalytic converter. But if you add the zddp additives to your oil for non-roller lifters, cams, or rockers and what not your catalytic converter will fail


True, but it takes a LONG time to fail, to my knowledge. They didn't severely cut back ZDDP until fairly recently to protect cats. Figure pretty much every car since 76 has had cats and high amounts of ZDDP... It doesn't seem like a big issue, to be honest I'm not sure why they make such a big deal about it. Likely something I don't know... You may want to put a short removable section in, where you can pull the after testing, just to be on the safe side. It's not required on your car so you don't have to have the cat all the time, but it'll be useful when being tested.


well thank you for your input

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