Deck 39: Emission Control Devices Operation and Diagnosis

Question 1

Two technicians are discussing clogged EGR passages. Technician A says clogged EGR passages can cause excessive NOx exhaust emission. Technician B says that clogged EGR passages can cause the engine to ping (spark knock or detonation). Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Answer 1

The exhaust gas recirculation (EGR) is an emission control system that lowers the amount of nitrogen oxides
formed during combustion. Excessive nitrogen oxide
is caused due to the clogged exhaust gas recirculation (EGR) passages. The clogged exhaust gas recirculation (EGR) passages may cause the engine to ping in other sense, spark knock, or detonation.
So, according to the above mentioned context, both technicians (technician A and technician B) are correct.
Therefore, the correct option is
.

Question 2

How does the use of exhaust gas recirculation reduce NOx exhaust emission?

Answer 2

The use of the EGR (exhaust gas recirculation) to reduce oxides of nitrogen
exhaust emission can be explained as follows:
The EGR (exhaust gas recirculation) is an emission control system that lowers the amount of oxides of nitrogen
formed during combustion. During the combustion process, nitrogen
and oxygen
molecules are separated into individual atoms of nitrogen and oxygen.
These molecules then combine to form oxides of nitrogen
. It can be carried out by the recirculation of a little amount (percentage) of the exhaust gases back into the intake. The process results in reduced combustion temperatures. The exhaust gases don not enter into the combustion process as they are chemically inert. This results into a lower peak combustion temperature and when the combustion temperature is lowered, the production of oxides of nitrogen is reduced.
When the EGR valve is opened, the exhaust gases flow through the valve and into the passages in the intake manifolds. The process can be clearly understood by figure shown below:
Figure 1

Question 3

An EGR valve that is partially stuck open would most likely cause what condition?

A) Rough idle/stalling
B) Excessive NOx exhaust emissions
C) Ping (spark knock or detonation)
D) Missing at highway speed

Answer 3

The exhaust gas re-circulation (EGR) valve when partially struck open would most likely cause the following condition:
The exhaust gas recirculation (EGR) is an emission control system that reduces the amount of nitrogen oxide
formed during the process of combustion. For the specified condition when the EGR valve is partially struck open will cause the condition of rough idle or stalling.
Therefore, the correct option is
.

Question 4

How does the DPFE sensor work?

Question 5

How much air flows through the PCV system when the engine is at idle speed?

A) 1% to 3%
B) 5% to 10%
C) 10% to 20%
D) Up to 30%

Question 6

What exhaust emissions does the PCV valve and SAI system control?

Question 7

Technician A says that if a PCV valve rattles, then it is okay and does not need to be replaced. Technician B says that if a PCV valve does not rattle, it should be replaced. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Question 8

How does a catalytic converter reduce NOx to nitrogen and oxygen?

Question 9

The switching valves on the AIR pump have failed several times. Technician A says that a defective exhaust check valve could be the cause. Technician B says that a leaking exhaust system at the muffler could be the cause. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Question 10

How does the computer monitor catalytic converter performance?

Question 11

Two technicians are discussing testing a catalytic converter. Technician A says that a vacuum gauge can be used and observed to see if the vacuum drops with the engine at 2,500 RPM for 60 seconds. Technician B says that a pressure gauge can be used to check for backpressure. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Question 12

At about what temperature does oxygen combine with the nitrogen in the air to form NOx?
a. 500°F (260°C)
b. 750°F (400°C)
c. 1,500°F (815°C)
d. 2,500°F (1,370°C)

Question 13

A P0401 is being discussed. Technician A says that a stuck-closed EGR valve could be the cause. Technician B says that clogged EGR ports could be the cause. Which technician is correct?

A) Technician A only
B) Technician B only
C) Both Technicians A and B
D) Neither Technician A nor B

Question 14

Which EVAP valve(s) is(are) normally closed?

A) Canister purge valve
B) Canister vent valve
C) Both canister purge and canister vent valves
D) Neither canister purge nor canister vent valve

Question 15

Before an evaporative emission monitor will run, the fuel level must be where?

A) At least 75% full
B) Over 25%
C) Between 15% and 85%
D) The level of the fuel in the tank is not needed to run [1]the monitor test