Deck 6: Exhaust Gas Composition and Analysis

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

Answer 1

A leaking fuel pressure regulator diaphragm

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

Answer 2

An open spark plug wire

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

Answer 3

B

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

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

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

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

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

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

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

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

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%

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

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

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)

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

Question 17

Which gas is considered toxic?

A) Carbon dioxide
B) Carbon monoxide
C) Oxygen
D) Nitrogen

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

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)

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