Deck 17: Exhaust Gas Recirculation

Question 1

Which of the following environmental problems is caused primarily by NOx emissions?

A)Global warming.
B)Global cooling.
C)Photochemical smog.
D)Soil contamination.

Answer 1

C

Question 2

Which combination of combustion conditions produces the highest NOx emissions from diesel engines?

A)High cylinder temperatures and pressures.
B)Rich air-fuel mixtures and low cylinder pressures.
C)High cylinder pressures and lean air-fuel mixtures.
D)Low soot and high cylinder temperature.

Answer 2

A

Question 3

To reduce NOx formation, which of the following combustion elements is replaced by EGR gas?

A)Nitrogen.
B)Nitric oxide (NO).
C)Oxygen.
D)Carbon dioxide (CO₂).

Answer 3

C

Question 4

Under which of the following conditions is EGR typically disabled?

A)Heavy acceleration and high engine loads.
B)After an active regeneration of the diesel particulate filter (DPF).
C)Excessively high engine coolant temperatures.
D)High barometric pressures.

Question 5

How does EGR gas contribute to increased cylinder wear?

A)It chemically weakens hardened steel piston rings.
B)It causes nitriding of piston rings.
C)It contains abrasive soot.
D)It retards injection timing.

Question 6

Which type of EGR system is used by the majority of automotive diesel engines?

A)Externally cooled EGR.
B)Internally cooled EGR.
C)Cooled, low-pressure EGR.
D)Cooled, high-pressure EGR.

Question 7

Technician A says that EGR systems lower in-cylinder NOx formation by reducing peak cylinder pressures and temperatures. Technician B says EGR systems reduce NOx emissions by reducing displaced air in the cylinder. Who is correct?

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

Question 8

Technician A says that turbocharger boost pressures are higher in EGR engines to compensate for power loss when using EGR gas. Technician B says that higher boost pressures are used to ensure that the combustion chamber receives an adequate amount of oxygen to support combustion. Who is correct?

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

Question 9

Technician A says the piston stroke length in an EGR engine is often longer than one in the same model engine that doesn't have an EGR system. Technician B says that the longer stroke length used by some EGR model engines has nothing to do with the use of EGR and that some EGR engines have shorter stroke length than non-EGR model engines. Who is correct?

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

Question 10

Technician A says that the oil used in the earliest EGR engines has a different API designation than oil used in engines with particulate filters. Technician B says that the oil used in engines equipped with particulate filters can be used in EGR engines. Who is correct?

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

Question 11

Technician A says that diesel engines that use EGR systems often have longer engine break-in periods. Technician B says that the use of EGR gas introduces abrasive soot into the cylinders, which shortens the break-in period. Who is correct?

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

Question 12

What device is used by internal EGR systems to force EGR gas into cylinders?

A)A variable-geometry turbocharger (VGT).
B)An exhaust pressure governor.
C)An EGR valve located between the exhaust and the intake manifold.
D)An additional bump on the exhaust camshaft lobe.

Question 13

Technician A says that internal EGR systems use a throttle plate to draw EGR gases into the air intake flow. Technician B says that high-pressure cooled EGR systems need throttle plates to draw exhaust gases into the intake manifold. Who is correct?

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

Question 14

Technician A says that EGR gas containing soot is present in all EGR systems. Technician B says that low-pressure EGR systems typically do not contain soot. Who is correct?

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

Question 15

What is the purpose of a mass airflow (MAF) sensor on an EGR-equipped engine?

A)To adjust air-fuel ratios on OBD-II compliant vehicles.
B)To meter the correct quantity of air required for combustion.
C)To measure the quantity of EGR gas entering engine cylinders.
D)To calculate precise air-fuel ratios.

Question 16

What does a temperature sensor combined with a delta P sensor measure?

A)EGR gas mass.
B)Exhaust backpressure.
C)Intake air mass.
D)Gas density.

Question 17

What happens to the mass of intake airflow into an engine when the EGR is enabled?

A)Nothing happens.
B)The mass increases.
C)The mass decreases.
D)The mass becomes cooler.

Question 18

Technician A says that diesel engines use MAF sensors to measure exhaust airflow into the cylinders. Technician B says that exhaust gas does not pass through an MAF sensor, so the MAF sensors cannot measure exhaust gas flow. Who is correct?

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

Question 19

Technician A says that oxygen sensors used by diesel engines adjust air-fuel ratios. Technician B says that oxygen sensors can be used to adjust the amount of EGR gas metered into the cylinders. Who is correct?

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

Question 20

While two technicians are discussing possible causes of engine coolant loss, Technician A says the EGR cooler is likely cracked and leaking. Technician B says that a cracked EGR cooler would leak coolant into the intake manifold. Who is correct?

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

Question 21

Which of the following environmental problems is caused primarily by NOx emissions?

A)Global warming."
B)Global cooling."
C)Photochemical smog.
D)Soil contamination."

Question 22

To reduce NOx formation, which of the following combustion elements is replaced by EGR gas?

A)Nitrogen."
B)Nitric oxide (NO)."
C)Oxygen.
D)Carbon dioxide (CO₂)."

Question 23

How does EGR gas contribute to increased cylinder wear?

A)It chemically weakens hardened steel piston rings."
B)It causes nitriding of piston rings."
C)It contains abrasive soot.
D)It retards injection timing."

Question 24

Technician A says that EGR systems lower in-cylinder NOx formation by reducing peak cylinder pressures and temperatures. Technician B says EGR systems reduce NOx emissions by reducing displaced air in the cylinder. Who is correct?

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

Question 25

Technician A says the piston stroke length in an EGR engine is often longer than one in the same model engine that doesn't have an EGR system. Technician B says that the longer stroke length used by some EGR model engines has nothing to do with the use of EGR and that some EGR engines have shorter stroke length than non-EGR model engines. Who is correct?

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

Question 26

EGR or exhaust gas recirculation is used to prevent the formation of:

A)NOx (oxides of nitrogen)"
B)HC (hydrocarbons)"
C)CO (carbon monoxide)
D)CO₂ (carbon dioxide)"

Question 27

EGR reintroduces exhaust gas into engine cylinders to reduce:

A)boost pressure"
B)intake pressure"
C)exhaust backpressure
D)peak cylinder pressure"

Question 28

Combustion temperatures above approximately what value can result in NOx?

A)1,500°F
B)2500°F"
C)2,000°F
D)500°F"

Question 29

The presence of a noxious reddish-brown tint to the atmosphere over cities when the winds are light indicates an abundance of:

A)Nitrous oxide (N2O)"
B)Nitrogen trioxide (NO3)"
C)Nitrogen dioxide (NO2)
D)Nitric oxide (NO)"

Question 30

NOx emissions forming during peak cylinder pressures and temperatures are reduced by extending the:

A)ignition delay period"
B)valve Timing"
C)burn period
D)injection timing"

Question 31

What device is used by internal EGR systems to force EGR gas into cylinders?

A)A variable-geometry turbocharger (VGT)."
B)An exhaust pressure governor."
C)An EGR valve located between the exhaust and the intake manifold.
D)An additional bump on the exhaust camshaft lobe."

Question 32

Which of the following is the EGR rate for a 2010 moderate diesel engines with an SCR (selective catalyst reduction)?

A)10-20%"
B)20-35%"
C)15-25%
D)35-50%"

Question 33

Which of the following is the EGR rate for a 2010 Navistar massive diesel engines without an SCR (selective catalyst reduction)?

A)10-20%"
B)20-35%"
C)15-25%
D)35-50%"

Question 34

All of these are types of EGR delivery systems that introduce exhaust gas uniformly into the cylinders used on light- and medium-duty diesels, EXCEPT one. Which one is that?

A)High-pressure cooled type"
B)Low-pressure cooled type"
C)Combined high- and low-pressure type.
D)Internal EGR"

Question 35

Technician A says that an internal EGR briefly opens the exhaust valve during the exhaust stroke. Technician B says that internal methods result in poor mixing with the intake air and excessive EGR rates at low speeds. Who is right?

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

Question 36

Which of the following measures pressure in the exhaust manifold?

A)Exhaust backpressure (EBP) sensor"
B)Manifold absolute pressure (MAP) sensor"
C)Mass air flow (MAF) sensor
D)Barometric pressure (BARO) sensor"

Question 37

Two technicians are describing high-pressure cooled (HP-CEGR) EGR systems. Technician A says that an HP-CEGR system does not use a throttle plate to draw exhaust in, instead a VGT pressurizes exhaust gases high enough to push exhaust into the boosted air intake. Technician B says that cooled EGR gas redirected from the exhaust manifold is pressurized to overcome intake boost pressure called high-pressure cooled EGR (HP-CEGR). Who is right?

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

Question 38

Which EGR system draws EGR gas into the cylinders through the turbocharger compressor inlet?

A)High-pressure cooled type"
B)Internal EGR"
C)External non-cooled
D)Low-pressure cooled type"

Question 39

Which of the following is NOT an advantage of using low-pressure exhaust gas recirculation?

A)Improved mixing of EGR and intake air"
B)Cleaner intake charge when drawing exhaust gas after the particulate filter"
C)Improved reduction in NOx emissions
D)Increased formation of corrosive combustion gas condensates"

Question 40

Two technicians are describing high- and low-pressure exhaust gas recirculation systems. Technician A says that non-cooled, high-pressure EGR flow dominates at low speed, low load conditions and transitions to more flow from the cooled, low-pressure EGR circuit. Technician B says that with an air intake throttle located downstream or after the EGR valve, the throttle plate can open and close to change the pressure differential. Who is right?

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

Question 41

What does a temperature sensor combined with a delta P sensor measure?

A)EGR gas mass."
B)Exhaust backpressure."
C)Intake air mass.
D)Gas density."

Question 42

Technician A says that diesel engines use MAF sensors to measure exhaust airflow into the cylinders. Technician B says that exhaust gas does not pass through an MAF sensor, so the MAF sensors cannot measure exhaust gas flow. Who is correct?

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

Question 43

While two technicians are discussing possible causes of engine coolant loss, Technician A says the EGR cooler is likely cracked and leaking. Technician B says that a cracked EGR cooler would leak coolant into the intake manifold. Who is correct?

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

Question 44

Which of the following forms closed-loop feedback with the EGR valve to regulate EGR gas flow?

A)Oxygen sensor"
B)MAP (manifold absolute pressure) sensor"
C)MAF (mass air flow) Sensor
D)BARO (barometric pressure) sensor"

Question 45

Which of the following mechanisms does NOT form a closed-loop feedback circuit for the EGR valve?

A)Using a MAP (manifold absolute pressure) sensor"
B)Using an MAF sensor"
C)Using a delta P sensor (pressure differential sensor)
D)Using oxygen sensors"

Question 46

Which of the following measures the pressure drop across a Venturi?

A)Delta pressure differential (delta P) sensor"
B)Barometric pressure (BARO) sensor"
C)Accelerator pedal position (APP) sensor
D)Manifold absolute pressure (MAP) sensor"

Question 47

Which of the following is NOT a requirement of EGR valve design features?

A)Increase formation of corrosive combustion gas condensates"
B)Minimize carbon contamination or coking in internal passageways"
C)Clean carbon contamination from the valve seat
D)Quicken response times to accurately meter exhaust gas flow"

Question 48

The cooler bundle is attached to the housing only through contact with:

A)straps"
B)expansion rods"
C)O-rings
D)struts"

Question 49

Two technicians are describing how to inspect an EGR cooler for leaks. Technician A says that you use shop air pressure regulated to 50 psi to pressurize the cooler exhaust ports to check for cracks. Technician B says that after visually inspecting the engine for coolant leaks during a pressure test, the EGR cooler can be disconnected and removed. Who is right?

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

Question 50

The cooler bundle on the 2.8 L Duramax is made up of:

A)aluminum tubes"
B)stainless steel tubes"
C)steel tubes
D)plastic tubes"

Question 51

Which of the following is required for EGR system diagnostics?

A)Vacuum gauge"
B)Vacuum pump"
C)Ruler
D)DMM (digital multimeter)"

Question 52

At idle, after the engine has warmed up, the vacuum signal to the EGR valve should be:

A)3-4 in Hg"
B)5-7 in Hg"
C)8-9 in Hg
D)1-2 in Hg"

Question 53

Two technicians are discussing EGR diagnostics. Technician A says that the onboard diagnostic (OBD) system monitors the EGR system for electrical and operational faults. Technician B says that the information from the EGR control pressure sensor can be read by a scan tool and should indicate atmospheric pressure with the key off. Who is right?

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

Question 54

Two technicians are discussing exhaust gas recirculation diagnostics. Technician A says that when diagnostic codes are set, the ECM will disable the EGR operation. Technician B says that significant differences between a sensed EGR control vacuum and a commanded vacuum signal will trigger diagnostic trouble codes. Who is right?

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

Question 55

Two technicians are discussing exhaust gas recirculation diagnostics. Technician A says that if any data are out of range or irrational when compared to other data, then the malfunction indicator lamp (MIL) will illuminate. Technician B says that several variables are monitored by the OBDII system of diesel EGR with the key off. Who is right?

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

Question 56

Two technicians are discussing EGR monitor. Technician A says that under the correct operating conditions, the OBD manager may briefly open the EGR valve and measure the drop in turbocharger speed against expected values. Technician B says that during monitoring, the turbocharger speed will drop because combustion temperature is cooler at low EGR flow rates. Who is right?

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

Question 57

What is measured by comparing exhaust temperature entering and leaving the cooler?

A)Cooler efficiency"
B)EGR efficiency"
C)Catalyst efficiency
D)Coolant efficiency"

Question 58

What test allows the service technician to override the EGR valve position by commanding different EGR valve positions and monitoring the actual position feedback from the valve?

A)EGR valve check"
B)DTC override"
C)EGR manual override
D)EGR automatic override"

Question 59

When should the VGT vanes or nozzle move from a closed to an open position?

A)At idle"
B)At full fuel"
C)At wide open throttle
D)At part throttle"

Question 60

Technician A says that EGR systems monitor engine speed and load conditions to meter the correct amount of exhaust gas into the engine intake. Technician B says that during idle, cold weather, or engine operation, maximum EGR flow usually takes place. Who is right?

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