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EMS-D All Chapters Studied > Week 3, Chapter 66 - Gasoline Exhaust Emissions > Flashcards

Week 3, Chapter 66 - Gasoline Exhaust Emissions Flashcards

1
Q

The air we breathe is composed of what two gases?

A

Nitrogen and Oxygen

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2
Q

Emission control systems are designed to do what?

A

Limit pollution

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3
Q

What causes emission pollution?

A

Storing and burning various fuels

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4
Q

Emissions from current gasoline-fueled motor vehicles usually come from three main sources…

A
  1. The fuel system
  2. The crankcase
  3. The tailpipe
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5
Q

Fuel vapors that escape into the atmosphere are called ________________

A

Evaporative emissions

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6
Q

Pollutants release from the exhaust in the form of gases called _______________________

A

Tailpipe emissions

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7
Q

Blowby gases from the crankcase that leak into the atmosphere are called _______________

A

Crankcase emissions

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8
Q

____ drive cycle is used to certify the emission output of vehicles and ensure they meet regulatory standards

A

FTP

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9
Q

EPA requires a ________________ to alert the driver of an emission system fault

A

Warning light

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10
Q

Regulated air pollutants can be divided into two groups:

A

Gases and particulates

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11
Q

Two categories of emissions:

A

Harmful and nonharmful

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12
Q

Water (H2O), nitrogen (N2) and oxygen (O2) are all examples of what category gas?

A

Nonharmful

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13
Q

Carbon monoxide (CO), hydrocarbons (HC), carbon dioxide (CO2), oxides of nitrogen (NOx), sulfur dioxide (SO2), and particulates are all examples of what category gas?

A

Harmful

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14
Q
  • Molecules of unburned gasoline
  • Evaporative fuel emissions also a source
  • When testing with a 5-gas analyzer readings should be less than 100ppm
A

Hydrocarbons (HC)

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15
Q
  • Fuel is absorbed into oil on cylinder walls
  • Fuel is not adequately mixed with air
  • Misfires
  • Very rich or lean mixtures that cause misfires

These are all causes of what?

A

Hydrocarbon emissions

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16
Q

_______________ is formed when carbon molecules join with oxygen molecules during combustion. Should be around 12-15%

A

Carbon dioxide

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17
Q
  • Part of the air in the air/fuel mixture
  • Not a pollutant
  • When testing with a 5-gas analyzer, levels should read 0-2%
A

Oxygen

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18
Q
  • A byproduct of combustion
  • Rich indicator
  • When using a 5-gas analyzer, readings should be less than 0.5%
A

Carbon monoxide

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19
Q
  • Formed when nitrogen and oxygen molecules combine at high temperature
  • A byproduct of excessive heat
  • Most accurately tested under a load
A

Oxides of nitrogen (NOx)

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20
Q

What are the main strategies used by companies to meet emission standards?

A
  • Design engine to reduce emissions
  • Control air-fuel mixture
  • Warm up engine quickly
  • Integrate precombustion and postcombustion
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21
Q

_______________________ focuses on assuring that combustion happens in a controlled and complete manner

A

Precombustion treatment

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22
Q

What are the two primary precombustion emission control systems?

A

Heated air intake system
Exhaust gas recirculation system

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23
Q

_______________________ systems deal with the remaining pollutants that are left over from the combustion process

A

Postcombustion emission control

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24
Q

What are the three primary postcombustion systems?

A
  • Positive crankcase ventilation (PCV)
  • Secondary air injection system
  • Catalyst system
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25
Q

Liquid fuel will not bur easily in the cylinder and must be in a ________ form for proper combustion

A

Vapor

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26
Q

Throttle body injection and carbureted systems may help ________ the exhaust through an intake crossover to help vaporize fuel

A

Route

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27
Q

_______________ use the air around hot exhaust manifolds to blend with outside air, to supply warm air at a predetermined temperature

A

Heated air intake systems

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28
Q

__________________ is used to preheat the engine during cold start

A

Cold start emissions reduction (CSER)

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29
Q

Exhaust gas recirculation (EGR) system is designed to do what?

A

Control oxides of nitrogen (NOx)

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30
Q

Newer engines use _______________ to draw some exhaust gases back into the cylinder

A

Variable valve timing

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31
Q

An ________________ connects a passage from the exhaust port, or manifold, to the intake manifold

A

EGR valve

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32
Q

What are the 5 gases that are tested in a 5-gas analyzer?

A
  1. Hydorcarbon (HC)
  2. Carbon Monoxide (CO)
  3. Nitrous Oxide (NOx)
  4. Carbon Dioxide (CO2)
  5. Oxygen (O2)
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33
Q

During combustion, an amount of fresh air-fuel mixture is replaced by _____________________

A

Inert exhaust gases

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34
Q

At wide-open throttle (WOT), the EGR system is typically ______________

A

Shut off

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35
Q

Older vehicles use _____________ solely to operate the EGR system

A

Vacuum controls

36
Q

Many vacuum controlled EGR systems also use a _______________________

A

Temperature-sensitive vacuum valve

37
Q

What are two common types of electric EGR valves?

A
  1. Pulse width modulated solenoid type
  2. Stepper motor EGR valve type
38
Q

What does the pulse width modulation system do?

A

Uses a spring-loaded valve that is opened by an electric solenoid and closed by the spring

39
Q

The stepper motor EGR valve controls _____________ much more precisely

A

EGR flow

40
Q

PCM sends signal to the stepper motor, which can do what?

A

Open or close the valve one step at a time

41
Q

Most PCM-controlled EGR systems incorporate a feedback loop, called a __________

A

Monitor

42
Q

What are the three main types of PCV systems?

A
  1. Variable orifice
  2. Fixed orifice
  3. Separator
43
Q

In which PCV system does a replaceable, spring loaded PCV valve regulate gas flow?

A

Variable orifice

44
Q

The PCV system is designed to remove blowby gases which may cause excessive ___________ emissions

A

Hydrocarbon

45
Q

Modern PCV systems are the ___________ type

A

Closed (sealed)

46
Q

What PCV system usually involves a screw-in fitting with a small hole drilled in it

A

Fixed orifice

47
Q

How does a fixed orifice type PCV system work?

A

The hole creates a predetermined vacuum leak that draws a predetermined amount of crankcase vapors from the crankcase

48
Q

What type of PCV system involves a valve that is hooked to the pressure side of the crankcase, an oil return line at the bottom of the valve, and a suction line on the other side?

A

Separator

49
Q

The separator type is used on _____________ applications

A

Turbocharged

50
Q

Secondary air injection post-combustion is less common nowadays because of…

A
  • Improved engine design
  • More accurate fuel delivery
  • Highly efficient three-way catalytic converters
51
Q

What three valves does a secondary air injection system use to control airflow in the system?

A
  1. Air switching valve
  2. Air diverter valve
  3. Check valve
52
Q

Early secondary air injection systems used a ___________________ in the vacuum line to control the switching valve

A

Thermal vacuum switch

53
Q

What is the main job of catalystic converters?

A

To perform a final cleanup of the tailpipe emissions

54
Q

What are the two types of catalytic converters?

A
  1. Oxidizing
  2. Reduction
55
Q

The ________ catalyst contains a platinum and rhodium coating, which helps to reduce the oxides of nitrogen molecules into their base compounds

A

Reduction

56
Q

More recent versions of the two-way (and three-way) catalytic converters are designed with a ___________ catalytic element

A

Honeycomb

57
Q

The PCM can control oxygen in the exhaust by adjusting the _________________

A

Air-fuel ratio

58
Q

The first oxygen sensor indicates the amount of oxygen in the exhaust stream as it leaves the ______________

A

Cylinders

59
Q

The second oxygen sensor measures the oxygen oxygen in the exhaust stream after it leaves the _______________________

A

Catalytic Converter

60
Q

The oxygen content is normally __________ after the converter and results in higher and steadier oxygen sensor voltage

A

Lower

61
Q

Catalytic _____________ happens when the catalyst becomes coated by a substance such as lead, silicone, or carbon

A

Contamination

62
Q

Catalytic __________ can cause the catalyst material to burn off the substrate, rendering it inoperative

A

Overheating

63
Q

Catalytic _________________ can happen due to an object such as a large rock striking the converter or from thermal shocks

A

Physical damage

64
Q

EVAP emission control systems are designed to ensure that…

A

Hydrocarbons are not released into the atmosphere

65
Q

EVAP system stores fuel vapors in the _____________ until the PCM’s command

A

Charcoal canister

66
Q

The fuel cap may incorporate a ____________________

A

Pressure relief valve

67
Q

Modern tanks also contain a(n) ______________________ that allows for the expansion of liquid fuel on hot days

A

Expansion volume

68
Q

A __________________ allows a space for liquid fuel to separate from the vapors and return to the fuel tank

A

Liquid-vapor separator

69
Q

What is the process of drawing fresh air up through the activated charcoal?

A

Purging

70
Q

What is the purpose of purging?

A

To prepare the canister to absorb fuel vapors the next time the vehicle is not running

71
Q

_______________________ is a critical part of reducing one of the major sources of hydrocarbon emissions

A

Capturing evaporated fuel vapors

72
Q

If a fuel is more __________, it is able to evaporate quickly and easily

A

Volatile

73
Q

Electronic controls in the EVAP system allow for more precise _____________________

A

Purge control

74
Q

Purge valve can be opened by an __________________ or __________________

A

Integrated solenoid
Stepper motor

75
Q

_____________ style can be either on/off or pulse-width-modulated

A

Solenoid

76
Q

In a _________________ style, the PCM can progressively open and close the purge valve one step at a time

A

Stepper motor

77
Q

A(n) ________ vapor control valve contains a float that rises with the fuel level and blocks off the vent hose when the tank is full

A

ORVR (Onboard Refueling Vapor Recovery)

78
Q

The first indication of any trouble with the emission system is a ____

A

MIL (Malfunction Indicator Light)

79
Q

Diagnosis of emission control systems starts with ________________

A

Verifying the concern

80
Q

The PCM’s ______________________ and data stream can also help identify faults

A

Freeze-frame data

81
Q

PCM’s _____________ capability may be helpful tooperate suspect components and observe the results

A

Bidirectional

82
Q

What tool uses sensors to measure the level of gases in the exhaust stream?

A

Five-gas analyzer

83
Q

Exhaust with a bluish tint means what?

A

Oil is being burned in the combustion chamber (piston oil control rings are worn)

84
Q

Exhaust with a black color means what?

A

Overly rich air-fuel mixture

85
Q

Exhaust with a white color means what?

A

Coolant is burning in the combustion chamber

EMS-D All Chapters Studied (11 decks)

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