Question 1

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):

$\begin{array} { l l l lr}
 \text {  At Idle:} &\quad\quad\quad& \text {At 2,500 RPM:  } \
 \mathrm { CO } _ { 2 } & = 8.10 \% &\quad\quad \mathrm { CO } _ { 2 } & = & 9.70 \% \ \mathrm { CO } & = 10.00 \%\text { (pegged high) } & \quad\quad\mathrm { CO } & = & 8.13 \% \ \mathrm { O } _ { 2 } & = 0.00 \% & \quad\quad\mathrm { O } _ { 2 } & = & 0.00 \% \ \mathrm { HC } & = 850 \mathrm { PPM } & \quad\quad\mathrm { HC } & = & 530 \mathrm { PP } \ \lambda & = 0.707&\quad\quad \lambda & = & 0.769 \end{array}$ 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 readings indicate a rich fuel mixture, as evidenced by high CO levels, low O2 levels, and a lambda value less than 1. A leaking fuel pressure regulator diaphragm would cause excess fuel to enter the engine, leading to these symptoms.

Question 2

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):

$\begin{array} { l l l lr}
 \text {  At Idle:} &\quad\quad\quad& \text {At 2500 RPM:  } \
 \mathrm { CO } _ { 2 } & = 8.35 \% &\quad\quad \mathrm { CO } _ { 2 } & = & 7.80 \% \ \mathrm { CO } & = 0.00 \% & \quad\quad\mathrm { CO } & = & 0.00 \% \ \mathrm { O } _ { 2 } & = 0.91 \% & \quad\quad\mathrm { O } _ { 2 } & = & 0.85 \% \ \mathrm { HC } & = 1,200 \mathrm { PPM } & \quad\quad\mathrm { HC } & = & 2,360\mathrm { PPM } \ \lambda & = 0.930 &\quad\quad \lambda & = & 0.908 \end{array}$ 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

An open spark plug wire would cause a misfire, leading to high HC levels and low CO and CO2 levels, as seen in the test results.

Question 3

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 corroded battery cable D) A cylinder misfire caused by a defective spark plug

Accepted Answer

A problem with the EGR (Exhaust Gas Recirculation) system can cause high levels of oxides of nitrogen (NOx) emissions because the EGR system is specifically designed to reduce NOx by recirculating a portion of an engine's exhaust gas back to the engine cylinders, lowering combustion temperatures.

Question 4

If a total misfire occurs within the cylinder for any reason, which gas levels will be dramatically high?
A) Carbon dioxide
B) Oxygen
C) Hydrocarbon
D) Carbon monoxide

Accepted Answer

The answer of If a total misfire occurs within the...

Question 5

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

An exhaust leak can cause both excessive CO (carbon monoxide) and O2 sensor (OS) readings to be out of the normal range, indicating a problem with the vehicle's ability to properly manage exhaust gases.

Question 6

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

Accepted Answer

Carbon monoxide (CO) is primarily produced from incomplete combustion, which occurs when there is not enough oxygen to produce carbon dioxide (CO2). This condition is most commonly associated with a rich air-fuel ratio, where there is more fuel than air available for combustion.

Question 7

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 8

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

Both water (H2O) and carbon dioxide (CO2) are by-products of the normal combustion process, making both Technician A and Technician B correct.

Question 9

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):

$\begin{array} { l l l lr}
 \text {  At Idle:} &\quad\quad\quad& \text {At 2,500 RPM:  } \
 \mathrm { CO } _ { 2 } & = 14.80 \% &\quad\quad \mathrm { CO } _ { 2 } & = & 8.30 \% \ \mathrm { CO } & = 0.00 \% & \quad\quad\mathrm { CO } & = & 0.00 \% \ \mathrm { O } _ { 2 } & = 0.20 \% & \quad\quad\mathrm { O } _ { 2 } & = & 4.25 \% \ \mathrm { HC } & = 45 \mathrm { PPM } & \quad\quad\mathrm { HC } & = & 330 \mathrm { PPM } \ \lambda & = 1.007 &\quad\quad \lambda & = & 1313\end{array}$ 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 A vehicle with a return-type fuel injection...

Question 10

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

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

Question 11

The term "stoichiometric" refers to an air fuel mixture of:
A) 16.5 to 1
B) 15.7 to 1
C) 14.7 to 1
D) 12 to 1

Accepted Answer

The term "stoichiometric" refers to the ideal air-fuel mixture where all the fuel is burned completely. For gasoline engines, this ratio is approximately 14.7 parts air to 1 part fuel, which is represented by choice C.

Question 12

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?
A) About 10%
B) About 21%
C) About 78%
D) About 90%

Accepted Answer

Ambient air consists of approximately 21% oxygen, so a properly functioning concentration-type gas analyzer should display a reading close to this percentage when exposed to ambient air.

Question 13

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 14

Constant volume sampling generally tests for which four gases? 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

Constant volume sampling typically tests for Carbon Monoxide (CO), Hydrocarbons (HC), Nitrogen Oxides (NOx), and Carbon Dioxide (CO2).

Question 15

Which gas can be used an indicator of a rich condition?
A) Carbon monoxide (CO)
B) Oxygen (O2)
C) Carbon dioxide (CO2)
D) Hydrogen (H)

Accepted Answer

Carbon monoxide (CO) is produced in higher quantities when there is a rich fuel mixture, meaning there is more fuel than oxygen during combustion. This is because there isn't enough oxygen to convert all the carbon in the fuel to carbon dioxide (CO2), resulting in the production of CO.

Question 16

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):

$\begin{array} { l l l lr}
 \text {  At Idle:} &\quad\quad\quad& \text {At 2,500 RPM:  } \
 \mathrm { CO } _ { 2 } & = 8.20 \% &\quad\quad \mathrm { CO } _ { 2 } & = & 14.30 \% \ \mathrm { CO } & = 0.00 \% & \quad\quad\mathrm { CO } & = & 0.00 \% \ \mathrm { O } _ { 2 } & = 5.10 \% & \quad\quad\mathrm { O } _ { 2 } & = & 0.25 \% \ \mathrm { HC } & = 1,200 \mathrm { PPM } & \quad\quad\mathrm { HC } & = & 30 \mathrm { PP } \ \lambda & = 1.304 &\quad\quad \lambda & = & 1.01 \end{array}$
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, which is indicated by the high oxygen content at idle and the lambda value of 1.304 (indicating a lean mixture). At 2,500 RPM, the engine is able to draw in more air, compensating for the vacuum leak, which is why the lambda value approaches 1.01 (nearly stoichiometric), and the oxygen content decreases.

Question 17

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

Accepted Answer

Carbon monoxide is considered toxic because it binds with hemoglobin in the blood more effectively than oxygen, reducing the blood's ability to carry oxygen and potentially leading to serious health effects or death.

Question 18

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

Accepted Answer

Carbon monoxide is a colorless, odorless gas, so Technician B is incorrect. Technician A is correct because carbon monoxide can cause dizziness, among other symptoms, due to its ability to prevent oxygen from binding to hemoglobin in the blood.

Question 19

Which gas can be used an indicator of a lean condition?
A) Carbon monoxide (CO)
B) Oxygen (O2)
C) Carbon dioxide (CO2)
D) Hydrogen (H)

Accepted Answer

Oxygen (O2) is used as an indicator of a lean condition because in a lean mixture, there is excess oxygen present after combustion since there isn't enough fuel to react with all the oxygen.

Question 20

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 gases will read higher than normal? A) HC B) CO C) CO₂ D) O₂

Accepted Answer

An exhaust system leak allows outside air, which contains oxygen (O₂), to enter the exhaust stream. This results in a higher than normal reading of O₂ in the exhaust gas analyzer.

Quiz 6: Exhaust Gas Composition and Analysis

A vehicle has high levels of oxides of nitrogen (NO_x) . Which condition could be the cause?

If a total misfire occurs within the cylinder for any reason, which gas levels will be dramatically high?

A vehicle has both excessive CO and O₂ readings. Which condition is the most likely cause?

Which statement is true about carbon monoxide (CO) ?

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?

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 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?

The term "stoichiometric" refers to an air fuel mixture of:

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?

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?

Constant volume sampling generally tests for which four gases?

Which gas can be used an indicator of a rich condition?

Which gas is considered toxic?

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?

Which gas can be used an indicator of a lean condition?

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 gases will read higher than normal?

Quiz 6: Exhaust Gas Composition and Analysis

A vehicle has high levels of oxides of nitrogen (NOx) . Which condition could be the cause?

If a total misfire occurs within the cylinder for any reason, which gas levels will be dramatically high?

A vehicle has both excessive CO and O2 readings. Which condition is the most likely cause?

Which statement is true about carbon monoxide (CO) ?

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?

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 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?

The term "stoichiometric" refers to an air fuel mixture of:

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?

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?

Constant volume sampling generally tests for which four gases?

Which gas can be used an indicator of a rich condition?

Which gas is considered toxic?

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?

Which gas can be used an indicator of a lean condition?

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 gases will read higher than normal?

A vehicle has high levels of oxides of nitrogen (NO_x) . Which condition could be the cause?

A vehicle has both excessive CO and O₂ readings. Which condition is the most likely cause?