Question 1

The ORVR system is designed to capture ________ during re-fueling.

Accepted Answer

The ORVR system, which stands for Onboard Refueling Vapor Recovery system, is specifically designed to capture fuel vapors that are emitted during the re-fueling process. This helps to prevent them from being released into the air, which can contribute to air pollution and smog.

Question 2

A state inspection of the EVAP system includes ________.

Accepted Answer

State inspection of the EVAP system includes both checking the fuel level in the tank and pressurizing the EVAP system. Additionally, they also test the gas cap for proper sealing. Therefore, the best choice would be D - both A and B.

Question 3

The EGR system is designed to lower which exhaust emission?

Accepted Answer

The EGR system is designed to lower nitrogen oxide (NOx) emissions, which is represented by "NO_x" in the options. The other options represent other exhaust emissions that are not controlled by the EGR system.

Question 4

All these are causes of catalytic converter failure EXCEPT ________.

Accepted Answer

Excessive water vapor is not a cause of catalytic converter failure, while contamination, incorrect air/fuel mixture, and excessive temperature are common causes. Water vapor, although it may impact the performance of the converter, is not typically a primary factor in its failure.

Question 5

Which exhaust emission is formed by high combustion chamber temperatures?

Accepted Answer

Nitrogen oxides (NOx), represented here as "NO_x" due to a formatting error, are formed at high combustion chamber temperatures.

Question 6

EGR is usually not required under which of these engine conditions?

Accepted Answer

EGR (Exhaust Gas Recirculation) is typically not required or is significantly reduced under conditions such as idle, wide open throttle, and when the engine is cold to ensure optimal engine performance and to prevent potential engine damage.

Question 7

Which type of EGR valve requires a positive exhaust system pressure to operate?

Accepted Answer

A positive backpressure EGR valve requires a positive pressure in the exhaust system to operate. This type of valve is commonly found in newer diesel engines with diesel particulate filters (DPF) and selective catalytic reduction (SCR) systems, which require a positive pressure to function properly.

Question 8

The following statements are all correct EXCEPT ________.

Accepted Answer

Low restriction exhaust systems can actually increase EGR flow and affect EGR system operation by altering exhaust backpressure. The other statements are correct.

Question 9

How many solenoids are contained in the GM digital EGR valve?

Accepted Answer

The GM digital EGR (Exhaust Gas Recirculation) valve contains three solenoids. These solenoids are used to precisely control the flow of exhaust gases back into the intake manifold, improving emissions and engine efficiency.

Question 10

All of the following statements are correct EXCEPT ________.

Accepted Answer

Linear EGR systems do not require exhaust backpressure as they control the amount of EGR flow based on the position of the EGR valve. The other statements are all correct.

Question 11

Which of the following are symptoms of a fault in the EGR system?

Accepted Answer

All of these symptoms could indicate a fault in the EGR (Exhaust Gas Recirculation) system. Detonation during acceleration or cruise can be caused by an overly lean air/fuel mixture, which may occur if the EGR valve is stuck open or the EGR system is not functioning properly. Rough idle and stalling can also be caused by a malfunctioning EGR valve or clogged EGR passages, as this can affect the engine's air/fuel ratio and cause irregular combustion. Excessive NOx emissions are also a sign of a problem with the EGR system, as the EGR system is designed to reduce NOx emissions by recirculating exhaust gas back into the engine.

Question 12

When performing an EGR system test on a vacuum operated EGR valve, how much should intake manifold vacuum decrease when the EGR valve is opened at fast idle?

Accepted Answer

When performing an EGR system test on a vacuum operated EGR valve, intake manifold vacuum should decrease by 6-8 in. Hg when the EGR valve is opened at fast idle. This indicates that the EGR system is functioning properly and that exhaust gases are being introduced into the combustion chamber.

Question 13

Technician A says that carbon should be cleaned out after installing a new EGR valve. Technician B cleans the EGR exhaust passages by using a stranded metal cable. Which technician is correct?

Accepted Answer

The answer of Technician A says that carbon should be...

Question 14

A vehicle comes into the shop and the technician retrieves the diagnostic code P0401 "EGR flow insufficient." Which of these could be the cause?

Accepted Answer

All of these could be the cause of an insufficient EGR flow. The EGR valve could be stuck open, the electrical wiring could be shorted, and/or the EGR ports or passages could be clogged. Further diagnosis and testing would be necessary to determine the exact cause.

Question 15

Technician A says that PCV valves should rattle when shaken. Technician B says that defective PCV systems may cause leaking engine seals. Which technician is correct?

Accepted Answer

Technician A is correct as the PCV valve should rattle when shaken. Technician B is also correct as a malfunctioning PCV system can cause increased crankcase pressure which can lead to oil leaks from engine seals.

Question 16

What term is used to describe combustion gasses leaking past cylinder rings?

Accepted Answer

Blow by is the term used to describe combustion gasses leaking past cylinder rings and into the crankcase.

Question 17

Technician A says that some crankcase vent systems use a calibrated orifice instead of a PCV valve. Technician B says that turbocharged engines often use an oil/water separator in the PCV system. Which technician is correct?

Accepted Answer

Both technician A and B are correct. Some crankcase vent systems use a calibrated orifice instead of a PCV valve, and turbocharged engines often use an oil/water separator in the PCV system to prevent oil from being forced into the intake system under boost.

Question 18

Technician A says that a 3 x 5 card should be held against the oil fill opening if the PCV system is operating correctly. Technician B says that if a PCV valve rattles, it definitely is good. Which technician is correct?

Accepted Answer

Technician A is correct. If the PCV system is operating correctly, holding a 3 x 5 card against the oil fill opening should create a vacuum and hold the card against the opening. Technician B is incorrect. Just because the PCV valve rattles, it does not mean that it is good. A PCV valve can rattle and still be stuck open, which would result in poor engine performance.

Question 19

Which component sends fresh air to the catalytic converter to help oxidize emissions?

Accepted Answer

The AIR pump (Air Injection Reactor) sends fresh air to the catalytic converter to help oxidize emissions. This process helps reduce harmful emissions from the engine. The PCV valve (Positive Crankcase Ventilation) is responsible for recycling the air that is in the engine's crankcase back into the intake manifold to be burned again, helping to reduce harmful emissions. The thermostatic air cleaner is responsible for controlling the temperature of the air entering the engine to improve fuel efficiency and performance, but it does not have a direct impact on emissions control. The EGR valve (Exhaust Gas Recirculation) recirculates a small amount of exhaust gas back into the engine to reduce the formation of harmful pollutants, but it does not specifically send fresh air to the catalytic converter.

Question 20

Which device protects the air pump from reverse exhaust pressure?

Accepted Answer

A check valve is designed to only allow air flow in one direction, preventing reverse exhaust pressure from damaging the air pump. The other three devices listed have different purposes and do not protect the air pump in this way.

Quiz 27: Emission Control Devices Operation and Diagnosis