Question 1

Which gas can be used an indicator of a rich condition?&#10;A)Carbon monoxide (CO)&#10;B)Oxygen (O&#8322;)&#10;C)Carbon dioxide (CO&#8322;)&#10;D)Hydrogen (H)

Accepted Answer

Carbon monoxide (CO) levels increase when there is incomplete combustion, which is a sign of a rich fuel mixture.

Question 2

The term &#34;stoichiometric&#34; refers to an air fuel mixture of:&#10;A)16.5 to 1&#10;B)15.7 to 1&#10;C)14.7 to 1&#10;D)12 to 1

Accepted Answer

Stoichiometric refers to the chemically balanced air-fuel mixture required for complete combustion. This typically refers to a mixture of 14.7 parts air to 1 part fuel by mass, also known as the "stoichiometric ratio" or "stoichiometric air-fuel ratio" (AFR). Choice C is the closest option to this ratio.

Question 3

When an engine has good combustion (proper compression and volumetric efficiency, proper spark timing and delivery, and a stoichiometric air-fuel ratio), which level of gas emissions should be high? A)CO emissions B)CO₂ emissions C)O₂ emissions D)NO_X emissions

Accepted Answer

When an engine has good combustion, it means that the fuel is being burned efficiently, resulting in minimal harmful emissions. However, CO2 (carbon dioxide) emissions will be high because CO2 is a natural byproduct of the complete combustion of hydrocarbon fuels. CO (carbon monoxide) emissions, NOx (nitrogen oxides) emissions, and other pollutants would be low in a well-functioning engine due to the efficient use of fuel and air, and proper catalytic converter function.

Question 4

An exhaust analyzer that measures lambda is being discussed. Technician A says a lambda reading of 0.98 to 1.02 is considered normal. Technician B says a lambda of 1.12 indicates a lean condition. Who is correct?

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

Accepted Answer

Lambda is a measure of the air-fuel ratio relative to the stoichiometric mixture. A lambda of 1 indicates a perfect stoichiometric mixture. Values between 0.98 and 1.02 are indeed considered normal, indicating a mixture very close to stoichiometric. A lambda greater than 1, such as 1.12, indicates more air than fuel, signifying a lean condition. Therefore, both technicians are correct.

Question 5

A vehicle with high levels of oxides of nitrogen (NOx)is being discussed. Technician A says engine overheating is a likely cause. Technician B says a defective turbocharger intercooler may be the cause. Who is correct?

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

Accepted Answer

A defective turbocharger intercooler can cause high levels of NOx emissions, but engine overheating is not a likely cause.

Question 6

When a concentration-type gas analyzer has been properly warmed up and its probe is exposed to ambient air, what should the displayed oxygen reading indicate?&#10;A)About 10%&#10;B)About 21%&#10;C)About 78%&#10;D)About 90%

Accepted Answer

The displayed oxygen reading should indicate about 21%, which is the approximate percentage of oxygen in ambient air at sea level.

Question 7

A vehicle has both excessive CO and O₂ readings. Which condition is the most likely cause? A)An intake manifold leak B)An exhaust leak C)A fuel injector leak D)An exhaust restriction

Accepted Answer

Excessive levels of CO and O₂ readings can be caused by an exhaust leak. The O₂ reading indicates that there is unburned oxygen in the exhaust, which occurs when exhaust gases leak out before they are fully burned. This unburned oxygen can also cause the excessive CO reading as it reacts with carbon monoxide and forms even more CO. Therefore, an exhaust leak is the most likely cause of these readings.

Question 8

Carbon monoxide (CO)is being discussed. Technician A says carbon monoxide may cause dizziness. Technician B says carbon monoxide smells like rotten eggs.Who is correct?&#10;A)Technician A only&#10;B)Technician B only&#10;C)Both A and B&#10;D)Neither A nor B

Accepted Answer

Carbon monoxide is an odorless gas, so Technician B is incorrect. However, Technician A is correct in stating that exposure to carbon monoxide can cause dizziness.

Question 9

Which gas is considered toxic?&#10;A)Carbon dioxide&#10;B)Carbon monoxide&#10;C)Oxygen&#10;D)Nitrogen

Accepted Answer

Carbon monoxide is considered toxic in high concentrations, as it can bind to hemoglobin and prevent oxygen from being transported in the blood. Carbon dioxide, oxygen, and nitrogen are not considered toxic gases in normal concentrations.

Question 10

A vehicle with a return-type fuel injection system is being tested with an exhaust gas analyzer and the following results are obtained (AIR pump disabled):
At Idle:                                                                        At 2500 RPM:
CO₂      =          8.20 %                                                 CO₂=          14.30 %
CO =          0.00 %                                                 CO =          0.00 %
O₂=          5.10 %                                                 O₂ =          0.25 %
HC =          1,200 PPM                                           HC       =          30 PP
L = 1.304 l =          1.01

Which condition would most likely be responsible for all of the readings shown?

A)An open spark plug wire
B)A vacuum leak
C)A restricted fuel filter
D)A leaking fuel pressure regulator diaphragm

Accepted Answer

A vacuum leak would cause a lean condition at idle, leading to high O2 and HC levels, and low CO2 levels. At higher RPMs, the effect of the vacuum leak is reduced, resulting in more normal readings.

Question 11

A vehicle with a return-type fuel injection system is being tested with an exhaust gas analyzer and the following results are obtained (AIR pump disabled):
At Idle: At 2500 RPM:
CO₂ = 14.80 % CO₂ = 8.30 %
CO = 0.00 % CO = 0.00 %
O₂ = 0.20 % O₂ = 4.25 %
HC = 45 PPM HC = 330 PPM
L = 1.007 l = 1.313

Which condition would most likely be responsible for all of the readings shown?

A)An open spark plug wire
B)A vacuum leak
C)A restricted fuel filter
D)A leaking fuel pressure regulator diaphragm

Accepted Answer

The answer of &#8203; A vehicle with a return-type fuel...

Question 12

A vehicle with a return-type fuel injection system is being tested with an exhaust gas analyzer and the following results are obtained (AIR pump disabled):
At Idle:                                                                        At2500 RPM:
CO₂= 8.10 % CO₂= 9.70 %
CO = 10.00 % (pegged high) CO = 8.13 %
O₂ = 0.00 % O₂ = 0.00 %
HC =      850 PPM HC =     530 PPM
L    = 0.707 l          = 0.769

Which condition would most likely be responsible for all of the readings shown?

A)An open spark plug wire
B)A vacuum leak
C)A restricted fuel filter
D)A leaking fuel pressure regulator diaphragm

Accepted Answer

The answer of &#8203; A vehicle with a return-type fuel...

Question 13

Which gas can be used an indicator of a lean condition?&#10;A)Carbon monoxide (CO)&#10;B)Oxygen (O&#8322;)&#10;C)Carbon dioxide (CO&#8322;)&#10;D)Hydrogen (H)

Accepted Answer

The answer of Which gas can be used an indicator...

Question 14

An exhaust gas analyzer (concentration sampling type)is being used to sample the exhaust of a vehicle that has an exhaust system leak. Which of these four gasses will read higher than normal? A)HC B)CO C)CO₂ D)O₂

Accepted Answer

The answer of An exhaust gas analyzer (concentration sampling type)is...

Question 15

A pre-OBD II vehicle with a return-type fuel injection system is being tested with an exhaust gas analyzer and the following results are obtained (AIR pump disabled):
At Idle:                                                            At 2500 RPM:
CO₂ = 8.35 % CO₂= 7.80 %
CO = 0.00 % CO       = 0.00 %
O₂= 0.91 % O₂ = 0.85 %
HC       = 2,150 PPM HC = 2,360 PPM
L = 0.930    l          = 0.908

Which condition would most likely be responsible for all of the readings shown?

A)An open spark plug wire
B)A vacuum leak
C)A restricted fuel filter
D)A leaking fuel pressure regulator diaphragm

Accepted Answer

The answer of &#8203; A pre-OBD II vehicle with a...

Question 16

Which statement is true about carbon monoxide (CO)?&#10;A)It is a result of too much combustion&#10;B)It is a result of a lean air fuel ratio&#10;C)It is a result of a misfire&#10;D)It is a result of a rich air fuel ratio

Accepted Answer

The answer of Which statement is true about carbon monoxide...

Question 17

Normal combustion is being discussed. Technician A says water (H₂O)is a by-product of normal combustion. Technician B says carbon dioxide (CO₂)is a by-product of normal combustion. Who is correct? A)Technician A only B)Technician B only C)Both A and B D)Neither A nor B

Accepted Answer

The answer of Normal combustion is being discussed. Technician A...

Question 18

Constant volume sampling generally tests for four gasses: A)O₂, N₂, HC, and CO₂ B)CO, HC, NO_x, and CO₂ C)NO_x, H₂O, CO₂, and CO D)NO_x, O₂, N₂, and H₂O

Accepted Answer

The answer of Constant volume sampling generally tests for four...

Question 19

A vehicle has high levels of oxides of nitrogen (NO_x). Which condition could be the cause? A)A rich air fuel mixture B)A problem with the EGR system C)A lean air fuel mixture D)A cylinder misfire caused by a defective spark plug

Accepted Answer

The answer of A vehicle has high levels of oxides...

Question 20

An engine has excessive oxygen (O₂)readings at idle. At 2500 RPM, the readings are normal. Which condition is the most likely cause? A)A restricted fuel filter B)A leaking fuel injector C)A vacuum leak D)A cracked spark plug

Accepted Answer

The answer of An engine has excessive oxygen (O₂)readings at...

Deck 6: Exhaust Gas Analysis