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1993 Volvo 940: Nitrogen Oxides Emissions

My 1993 Volvo 940 recently passed its California smog emissions test except for Nitrogen Oxides (NOx). The test pass level for NOx is 486 ppm max. My car emitted 521 ppm of NOx. I suspect that there may be a problem with the EGR System, (e.g., clogged valve, bad temperature sensor, etc.) Any advice will be greatly appreciated... I do not believe that the issue has anything to do with the Catalytic Converter as the Hydrocarbon % was well within the test limits.

Many thanks,

OnlyVolvo








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1993 Volvo 940: Nitrogen Oxides Emissions

Could be as EGR cools combustion; however, my 93 Regina 940 does not have the EGR. Maybe California did. If so, I'd make sure I works, otherwise, you could be looking at a converter, I think.







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