Which indicates a functioning EGR valve during testing?

Which indicates a functioning EGR valve during testing?

• A. Engine RPM drops when vacuum is applied to the EGR valve.
• B. Engine RPM rises when vacuum is applied to the EGR valve.
• C. Engine RPM remains constant when vacuum is applied.
• D. Engine stalls when vacuum is applied.

Answer: (A)

This test checks whether the EGR valve responds to a vacuum signal. When the valve is functioning, applying vacuum to it should cause the valve to open and allow exhaust gas to recirculate into the intake. That additional gas reduces the effective air for combustion, and at idle the engine typically slows down. So a drop in engine RPM while vacuum is applied indicates the EGR valve is opening and working properly. If the RPM stays the same or increases, the valve isn’t opening as it should, suggesting a malfunction or vacuum issue. If the engine stalls when vacuum is applied, that can point to excessive or uncontrolled EGR flow or other vacuum problems, which again means the valve isn’t functioning correctly.

This test checks whether the EGR valve responds to a vacuum signal. When the valve is functioning, applying vacuum to it should cause the valve to open and allow exhaust gas to recirculate into the intake. That additional gas reduces the effective air for combustion, and at idle the engine typically slows down. So a drop in engine RPM while vacuum is applied indicates the EGR valve is opening and working properly. If the RPM stays the same or increases, the valve isn’t opening as it should, suggesting a malfunction or vacuum issue. If the engine stalls when vacuum is applied, that can point to excessive or uncontrolled EGR flow or other vacuum problems, which again means the valve isn’t functioning correctly.