7.   Technician A says that manually opening an exhaust gas recirculation (EGR) valve with a vacuum pump or scan tool will cause the engine to idle roughly or stall. Technician B says that blocking the EGR valve passages will have no effect on the OBD-II. Who is correct?

8.   Oxides of nitrogen (NOx) contribute to the formation of

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7.   Technician A says that manually opening an exhaust gas recirculation (EGR) valve with a vacuum pump or scan tool will cause the engine to idle roughly or stall. Technician B says that blocking the EGR valve passages will have no effect on the OBD-II. Who is correct?

8.   Oxides of nitrogen (NOx) contribute to the formation of

Technician A is correct.

Opening the exhaust gas recirculation (EGR) valve manually with a vacuum pump cause the engine to roughly idle or stall. This is because the exhaust gas is recirculated to the engine intake valve and improve the performance by exchanging heat with the fresh air.

The statement of technician A is correct. While the technician B statement says incorrect. The blocking of EGR valve passages causes problems in the engine performance. This is also diagnosed on the OBD-II.

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