Exam 33: Emission Control Systems

Technician A says high engine temperatures reduce HC and CO emissions. Technician B says incorrect ignition timing can increase the production of NO_X.Who is correct?

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?

An I/M 240 test lasts _____ minutes.

Describe the operation of a digital EGR valve.

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

The PCV system prevents ____________________ gases from escaping to the atmosphere.

Diesel engines emit less HC, CO, and CO₂ than spark ignition gasoline engines.

Technician A says a three-way catalytic converter [TWC] oxidizes carbon monoxide and hydrocarbons into carbon dioxide and water. Technician B says a TWC reduces NO_x into nitrogen and carbon dioxide. Who is correct?

The technical term for the soot or the black smoke emitted from a diesel's exhaust pipe is _________________.

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

Large amounts of CO₂ in the exhaust are desirable.

NO_X emissions increase as combustion temperatures increase.

Technician A says the air control valve (or air-switching valve) is a vacuum-operated valve that routes the air from the pump either to the exhaust manifold or to the catalytic converter. Technician B says the air bypass (AIRB) valve (or diverter [AIRD] valve) located between the air pump and the air control valve diverts the air pump output to the atmosphere or air filter during deceleration. Who is correct?

Which of the following is NOT related to photochemical smog?

Which of the following systems is designed to reduce NO_X?

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

What is an I/M 240 test?

Technician A says the OBD-II EVAP system leak test monitor will not run if the fuel level is too high. Technician B says the monitor will not run if the fuel level is too low. Who is correct?

The EVAP systems use a ____________________ canister to collect fuel vapors until they can be purged.

NO_X, HC, and CO are changed into harmless gases by the ____________________ in the three way catalytic converter.