Exam 33: Emission Control Systems

Technician A says the production of CO₂ is directly related to the amount of fuel consumed; therefore, more fuel-efficient engines produce less CO₂. Technician B says imposing new CAFE (fuel economy)standards will, in effect, reduce CO₂ emissions. Who is correct?

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?

Diesel engines use a PCV system that is nearly identical to a gasoline engine's PCV system, but is designed for a greater rate of flow.

Excessive oxygen in the exhaust indicates an improper air/fuel mixture.

Carbon monoxide is being discussed. Technician A says as the air/fuel ratio becomes richer, the CO levels decrease. Technician B says CO is a colorless, odorless, and highly poisonous gas that can cause death. Who is correct?

Technician A says diesel fuel 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?

Technician A says HC emissions are caused by incomplete combustion. Technician B says an excessively lean air/fuel mixture may result in cylinder misfiring and high HC emissions. Who is correct?

Hydrocarbon and carbon monoxide exhaust emissions are highest when the engine is cold.

Which of the following systems is designed to reduce NO _X ?

The I/M 240 test requires the use of a  variable inertia weight  ____________________.

The enhanced evaporative emission system (OBD-II)can detect a leak in the hoses, lines, fuel tank, or gas cap as small as _____ in.

Technician A says the DPFE (differential pressure feedback EGR)sensor determines the amount of gas flowing through the EGR valve by measuring the pressure drop across an orifice. Technician B says some EGR valves have an NTC thermistor that measures exhaust gas temperature at the outlet of the EGR valve. Who is correct?

_____ emissions are caused largely by unburned fuel from the combustion chambers.

Large amounts of CO₂ in the exhaust are desirable.

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?

Why are heated PCV valves used on some vehicles?

Technician A says the EGR vent solenoid is normally open. Technician B says the EGR control solenoid is normally open. Who is correct?

Port fuel injected engines require intake manifold heating devices.

The normal operating temperature for most catalytic converters is about ______.

Which of the following is NOT related to photochemical smog?