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1977 Chevy Blazer Failed Smog Test High CO

My Chevy Blazer failed the smog check for high CO. It tested 3.80 at 15mph and 3.09 at 25 mph max for the 15mph is 2.66 and at 25 the max is 2.52.

I readjusted the carburetor. Should I go to a smaller jet or chance the smog retest and see where I'm at. What's the best way to go about getting my Blazer to pass the smog check? I never had this problem before this year's emissions test.

Answer:

It seems your Chevy Blazer is running very rich. The right way to adjust the carburetor is by using a 5 gas analyzer or a BAR-97 smog machine. Adjusting the carb via the mixture screws by "number of turns" or by listening to engine misfires will do no good when it comes time to smog check. Fine adjustments are needed in order to set 14.7:1 air/fuel ratio. By using a gas (exhaust) analyzer you'll be able to accurately adjust your Blazer's carburetor to get passing smog check results. If you feel the carburetor is not the cause of your Blazer's high CO fault don't forget to look at the basics like engine compression and/or possibly any condition which can introduce fuel to the intake manifold bypassing the carburetor, such as a faulty EVAP system. posted by SmogTips Support

You may also consider rebuilding your Chevy Blazer's carburetor. However keep in mind that to will require fine tuning. Often times vehicle owners assume that a carburetor rebuild shop will adjust the carburetor prior to returning it to the owner. The carb rebuild shop can not fine tune a carburetor until it has been installed on the engine it came off of. Only then will they be able to, using a gas analyzer, measure the amount of HC and CO the engine is producing based on the carburetor high and low adjustments. posted by SmogTips Support

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