Exam 33: Emission Control Systems

HC and NO_X emissions exposed to sunlight in stagnant air produce ____________________.

Describe the purpose of the EGR system.

A digital EGR valve contains up to three electric solenoids that are operated directly by the PCM.

Why are heated PCV valves used on some vehicles?

The first controlled automotive emission was ______.

Most current light-duty diesel engines use a ___________________ rail injection system.

Technician A says there is maximum EGR flow only when the vehicle is at a cruising speed with a very light load. Technician B says instead of an EGR valve many late-model engines use variable valve timing [VVT] to trap some exhaust gases in the combustion chamber. Who is correct?

How is acid rain related to automotive emissions?

The AIR system reduces ______.

Technician A says diesel fuel is a light fuel oil and is denser [heavier] than gasoline. Technician B says diesel fuel is not as good a lubricant as gasoline; therefore wear on piston rings and cylinder walls is a greater problem for diesel engines. Who is correct?

Carbon dioxide [CO₂] is a greenhouse gas and may be the major cause of global warming.

A linear EGR valve contains up to three electric solenoids that are operated directly by the PCM.

Lower compression ratios reduce NO_X emissions.

EGR flow is disabled during throttle openings of more than ___________________ percent

Technician A says electronic secondary air systems used on OBD-II vehicles use an electrically driven air pump. Technician B says the check valves in the secondary air tubes prevent converter overheating if the electric air pump fails. Who is correct?

The exhaust gas recirculation system reduces ______.

Which of the following is NOT part of an enhanced [OBD-II] evaporative control system?

All the following are considered harmful gases EXCEPT:

A catalytic converter is one of the most effective emission control devices on a vehicle for reducing HC, CO, and NO_X emissions.

Technician A says oil in the PCV filter and air cleaner can occur if the PCV valve is restricted or plugged. Technician B says oil buildup inside the throttle body can be an indication of high crankcase pressure. Who is correct?