Technician A says that engine vacuum is used to operate some emissions control devices. Technician B says that an EGR valve may be operated by engine vacuum. Who is correct?

Question

Quizplus · Accepted Answer

Both technicians are correct. Engine vacuum is used to operate many emissions control devices, such as the PCV valve and the vacuum advance on older cars. An EGR valve can also be operated by engine vacuum to let in exhaust gases back into the engine to reduce NOx emissions.

Technician a Says That Engine Vacuum Is Used to Operate