If the EGR valve is not functioning, what emission is more likely to increase during an ASM Smog test?

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Prepare for the California BAR Smog Technician Test. Review key topics with flashcards and multiple choice questions, each question includes hints and explanations. Get ready to ace your exam!

Multiple Choice

If the EGR valve is not functioning, what emission is more likely to increase during an ASM Smog test?

Explanation:
EGR’s job is to lower NOx by recirculating a portion of exhaust gas back into the intake, which dilutes the air–fuel mixture and reduces peak combustion temperature. When the EGR valve isn’t functioning, that cooling and dilution don’t happen, so combustion temperatures stay higher and NOx formation increases. During an ASM Smog test, NOx is the pollutant most directly affected by a nonworking EGR, whereas CO and HC are more tied to combustion quality and timing, and PM is not the primary concern for a typical gasoline engine in this context. So NOx rises.

EGR’s job is to lower NOx by recirculating a portion of exhaust gas back into the intake, which dilutes the air–fuel mixture and reduces peak combustion temperature. When the EGR valve isn’t functioning, that cooling and dilution don’t happen, so combustion temperatures stay higher and NOx formation increases. During an ASM Smog test, NOx is the pollutant most directly affected by a nonworking EGR, whereas CO and HC are more tied to combustion quality and timing, and PM is not the primary concern for a typical gasoline engine in this context. So NOx rises.

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