Deck 34: Emission Control Diagnosis and Service

Question 1

A catalytic converter can be tested with a rubber mallet.

Answer 1

True

Question 2

Excessive carbon monoxide [CO] forms when there is not enough O₂ to combine with the carbon during combustion.

Answer 2

False

Question 3

An alternative to the I/M 240 test is the acceleration simulation mode (ASM) test.

Answer 3

True

Question 4

If the engine stalls at idle when the EGR is fully opened, the EGR system can be assumed to be working at peak efficiency.

Question 5

A restricted catalytic converter may cause ______.

A) loss of power at high speeds
B) stalling after starting
C) a drop in engine vacuum as engine rpm increases
D) all answers are correct

Question 6

A scan tool can be used to diagnose a faulty ______.

A) knock sensor
B) EVR solenoid
C) EVAP system
D) all answers are correct

Question 7

Which of the following is a cause of detonation?

A) a disconnected EGR valve vacuum line
B) a leaking EGR valve diaphragm
C) the EGR valve stuck in the closed position
D) all answers are correct

Question 8

An AIR system should be checked for overall efficiency by looking at the changes in exhaust quality when the system is turned on and off.

Question 9

Which of the following gases is NOT considered to be harmful?

A) HC
B) CO
C) O₂
D) NO_X

Question 10

A catalytic converter can be tested by measuring the inlet and outlet temperatures.

Question 11

A stuck closed PCV valve or restricted hose may cause an accumulation of moisture and sludge in the engine.

Question 12

All EGR valves can be tested with a vacuum gauge while the engine is idling.

Question 13

Excessive oil consumption can be caused by a plugged PCV hose.

Question 14

During an I/M 240 test, the vehicle's exhaust is collected by a CVS system.

Question 15

Poor EGR gas flow can cause detonation (spark knock).

Question 16

Which of the following emission systems is typically NOT controlled by the PCM?

A) EGR system
B) EVAP system
C) AIR system
D) PCV system

Question 17

If the PCV valve is stuck in the open position, a lean air/fuel ratio may cause a rough idle or engine stalling.

Question 18

Low CO indicates a lean mixture; as the mixture becomes more lean, HC increases.

Question 19

A catalytic converter may be tested with a ______.

A) pyrometer
B) rubber mallet
C) vacuum gauge
D) all answers are correct

Question 20

Which of the following may result from too little EGR flow?

A) The engine may overheat
B) The engine may detonate
C) The engine may emit an excessive amount of NO_X
D) All answers are correct

Question 21

Technician A says when CO goes up, O₂ goes down.Technician B says at the stoichiometric point [14.7:1], HC and CO will be at their lowest levels and CO₂ will be at its highest. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 22

Technician A says an I/M 240 test is four minutes long. Technician B says the test cycle includes acceleration, deceleration, and cruising on an actual road test. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 23

Technician A says cylinder misfiring causes a significant increase in HC emissions. Technician B says a dirty air filter may cause high CO emissions. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 24

Excessively high HC emissions may be caused by ______.

A) ignition system misfiring
B) an improper ignition timing
C) a lean air/fuel ratio
D) both "ignition system misfiring" and "an improper ignition timing"

Question 25

A typical four-gas exhaust analyzer does not measure ____ emissions.

A) CO
B) CO₂
C) HC
D) NO_X

Question 26

Technician A says the AIRB valve directs secondary air either to the intake manifold or to the catalytic converter. Technician B says with the engine at normal operating temperature, the AIR system sometimes goes back into upstream mode with the engine idling. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 27

Excessively high CO emissions may be caused by a ______.

A) lean air/fuel mixture
B) missing air filter
C) higher than normal fuel pressure
D) all answers are correct

Question 28

Crankcase pressure forcing crankcase gases through the clean air hose and into the air cleaner is being discussed. Technician A says the cause may be an excessive amount of blowby. Technician B says the cause may be a restricted PCV valve. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 29

The customer complains of a loss of power at highway speeds and a rough running engine at all speeds. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 700 ppm, CO = 0.2%, CO₂ = 9.2%, O₂ = 6.2%, and NO_X = 330 ppm. What is the most likely cause?

A) rich mixture
B) lean mixture
C) lean misfire
D) ignition misfire

Question 30

Technician A says a defective throttle position (TP) sensor will not affect the EGR valve operation. Technician B says a defective engine coolant temperature (ECT) sensor will not affect the EGR valve operation. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 31

While discussing catalytic converter diagnosis, Technician A says a delta temperature test should be conducted. Technician B says a good converter is evident by low amounts of CO₂ in the tailpipe exhaust. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 32

A vehicle is in the shop because it failed an emissions test due to excessive carbon monoxide [CO]. The fault was a bad oxygen sensor that was easily replaced. Technician A says that the EGR system should be checked before the vehicle is retested. Technician B says the vehicle should be tested with a five-gas analyzer before it is retested. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 33

When the engine is running at peak efficiency, the only gas that is desirable to be at its peak level is ______.

A) CO
B) CO₂
C) HC
D) O₂

Question 34

Technician A says CO emissions increase as the air/fuel ratio becomes richer. Technician B says CO emissions increase as the air/fuel ratio becomes leaner. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 35

Technician A says a defective PCV valve may cause rough idle operation. Technician B says the PCV system depends upon a properly sealed engine to perform correctly. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 36

Technician A says if the EVAP system is purging vapors from the charcoal canister while the engine is idling, rough engine operation will occur. Technician B says the system should not have more than 0.5 liter of flow during the 240 seconds of an I/M 240 test. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 37

Technician A says a pressure gauge can be inserted into the oxygen sensor bore, and back pressure caused by the catalytic converter can be measured. Technician B says a vacuum gauge can be used to identify a restricted converter. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 38

Technician A says if the EGR valve does not open, the engine may emit excessive amounts of HC. Technician B says if the EGR valve does not open, the engine may detonate on acceleration. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 39

Technician A says retrieving DTCs from the control system is the best beginning for diagnosing emission problems. Technician B says because a single emissions system component failure can set multiple DTCs, codes should be used only to confirm the effectiveness of the repairs. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 40

To monitor the vapor purge in most systems, the PCM changes the duty cycle of the purge solenoid while monitoring the ______.

A) STFT
B) LTFT
C) MAP voltage
D) MAF voltage

Question 41

Some AIR systems will set a ___________________ in the PCM if there is a fault in the system.

Question 42

An exhaust ___________________ is one of the valuable diagnostic tools for driveability problems.

Question 43

A restricted or plugged ___________________ system may cause excessive HC and CO emissions.

Question 44

In an engine in good condition running at 2,000 rpm, with a working EGR system, NO_X should be below _____ ppm.

A) 100
B) 200
C) 1,000
D) 1,750

Question 45

A stuck open EGR valve could cause _____.

A) stalling
B) excessive NO_X emissions
C) engine knock [detonation]
D) all answers are correct

Question 46

High ___________________ emissions are associated with an inoperative EGR valve.

Question 47

A dirty air filter may cause lower than normal ___________________ emissions.

Question 48

The customer complains of poor fuel economy. A five-gas analyzer reveals these measurements at 2,500 rpm: HC = 72 ppm, CO = 3.2%, CO₂ = 10.3%, O₂ = 0.2%, and NO_X = 122 ppm. What is the most likely cause?

A) rich mixture
B) lean mixture
C) lean misfire
D) ignition misfire

Question 49

Technician A says a loose oil filler cap or a dip stick that is not fully seated in the dipstick tube can change the LTFT on a MAF system. Technician B says the PCV system will draw unfiltered air through these leaks which could result in premature wear of engine parts. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 50

Before the EVAP system on an OBD-II vehicle can be pressure tested or smoke tested for leaks, a scan tool must be used to _____.

A) close the IAC valve on the throttle body
B) reset the EVAP flow rate monitor
C) open the canister purge solenoid
D) close the canister vent solenoid

Question 51

Higher than normal ____________________ emissions may be caused by an overheated engine.

Question 52

Spark knock may be referred to as ____________________.

Question 53

An excessively lean air/fuel ratio resulting in misfires causes HC emissions to ____________________.

Question 54

The first time the OBD-II system monitor detects a fault in the system, a ___________________ DTC is set. This will not cause the MIL light to illuminate and will self-erase if the monitor passes on the next trip.

Question 55

Excessively high ____________________ emissions can be caused by any condition that prevents the EGR from allowing the correct amount of exhaust gases to enter the cylinders.

Question 56

The OBD-II EGR system monitor tests the functioning of the EGR system by opening the EGR valve while monitoring the change in ______.

A) STFT
B) EGR outlet temperature
C) MAP voltage
D) all answers are correct

Question 57

What tool is needed to test a digital EGR valve?

A) scan tool
B) a 0.020 inch pin gauge
C) jumper wires
D) all answers are correct

Question 58

What tool is needed to test vacuum-type EGR valves?

A) digital pyrometer
B) feeler gauge
C) hand vacuum pump
D) all answers are correct

Question 59

A rich air fuel mixture will cause high ____________________ emissions.

Question 60

Technician A checks a PCV valve by sucking air through it with his mouth. Technician B checks a PCV valve by removing the valve from the grommet in the valve cover and placing his finger over the end of the valve to check for vacuum. Who is correct?

A) A only
B) B only
C) both A and B
D) neither A nor B

Question 61

A water manometer for testing crankcase pressure/vacuum can be made from a 2 foot length of _____________________.

Question 62

Starting with the 2000 model year, the new EVAP monitor system is designed to detect leaks as small as ___________________ inch.

Question 63

Nearly all OEMs recommend ___________________ rather than compressed air for pressure testing the EVAP system because it does not support combustion and is unlikely to cause an explosion.

Question 64

What can result from a charcoal canister saturated with gasoline?

Question 65

What will result from too little EGR flow?

Question 66

What is an OBD-II monitor?

Question 67

Identify the two causes of lower than normal CO₂ emissions.

Question 68

Identify the causes of high HC emissions.

Question 69

What happens if a PCV valve is stuck in the open position?