Emissions Control Systems and Components
Warm-up converter (WUC)
The purpose of this device is to reduce some of the exhaust emissions before the main catalytic converter has warmed to operating temperature.
Thermostatic air cleaner
The purpose of this emissions control system is to warm the intake air for better fuel atomization, so leaner air-fuel mixtures can be used on startup.
Vacuum solenoid valve (VSV)
The purpose of this valve is to block the vacuum signal to the distributor advance unit during low speed operation.
Soapy water
To check the air injection system for leaks, spray all hose connections and joints with...
Inert gas
To control combustion chamber temperatures, the intake air-fuel mixture can be diluted with...
1969
Closed PCV systems were required as of what vehicle model year?
Charcoal
Purging refers to the process of pulling fresh air through the canister, which forces fuel vapors out of the...
Rich
Quickly closing the throttle at high engine speeds results in an air-fuel mix that is very...
Kinked or burned
Route PCV hoses so they do not get...
Orifice spark advance control (OSAC) valve
Some Chrysler vehicles use this valve between carburetor ported vacuum and the distributor advance unit to delay vacuum advance.
Gulp valve
Some air injection system use this valve to divert pressurized air into the intake manifold during high speed deceleration.
Vented into the PCV system and stored inside the crankcase
Some early EVAP systems didn't use a charcoal canister. Instead, fuel fumes were...
Ambient air temperature sensor
Some vacuum spark advance systems that do not use a coolant temperature override switch use this sensor.
A clicking or ratting noise should be heard
Stop the engine and remove the PCV valve. Shake the valve. What should you observe?
High
When an engine is at idle, the vacuum signal to the PCV valve is...
Blocked off
When coolant temperature is low, vacuum signal to the EGR valve is...
1970
When did California prohibit the venting of fuel vapors to atmosphere?
1961
When did California start requiring PCV systems on passenger cars?
1963
When did Federal regulations require PCV systems on cars?
1950s
When did the first PCV systems appear on vehicles?
Cruise
When does maximum PCV flow rate occur?
20%
When fuel vapors were vented to atmosphere, what percentage of vehicle hydrocarbon emissions came from these vents?
Held closed by the diaphragm spring
When gasoline engines are at WOT (little to no vacuum in the intake manifold), the EGR valve is...
If the canister cracks, is damaged in any way, or becomes saturated with fuel
When should the charcoal canister be replaced?
7-14 in H2O (0.5-1.0 in Hg)
When testing the PCV system using a water manometer connected to the oil dipstick tube, how much vacuum should be measured?
Increase
When testing the air injection pump, accelerate the engine to 1500 RPM and observe air flow from hoses. As engine speed increases, air flow should...
The canister should not hold vacuum
When testing the charcoal canister, the vent lines to the canister are plugged and a vacuum pump is attached at the purge line port. Vacuum is applied. What should happen?
Closed
When the breather that allows air into the crankcase is connected to the air cleaner, the system is considered...
Open
When the breather that allows air into the crankcase is vented to atmosphere, the system is considered...
Vacuum
When the exhaust valves close, gases flowing out of the system form...
High
When the exhaust valves open, exhaust pressure is very...
Exhaust gases
When the pulse air check valve closes in response to exhaust pressure peaks, it prevents the flow of what up the air tube?
EGR operation
When the throttle plate opens, more of the port is exposed to manifold vacuum, increasing...
Positive backpressure EGR valve
When this part receives sufficient exhaust backpressure, it closes the air bleed hole, so maximum attainable vacuum is applied to the diaphragm, and the EGR valve opens.
1971
When was it federally prohibited to vent fuel vapors to atmosphere?
Air injection lines
Where are the check valves in the air injection system located?
Under the carburetor
Where is the preheating grid located?
HC and CO
Which harmful emissions are reduced by using air injection systems?
To sense coolant temperature, and block the vacuum signal to the EGR valve until a specific engine temperature is reached
Why do most EGR systems on gasoline engines use a temperature valve of some type?
To heat the catalytic converter to operating temperature sooner
Why do some air injection systems inject fresh air into the catalytic converter upon vehicle startup?
To avoid excessive pressure at high engine speed and to limit the amount of air injected
Why is a pressure relief valve used on pump style air injection systems?
To reduce hydrocarbon emissions which contribute to photochemical smog
Why were evaporative emissions control systems developed?
Heat from the exhaust manifold
With a fresh supply of oxygen injected close to the exhaust valves, what ignites the mixture of oxygen and unburnt fuel?
Engine speed and engine vacuum
With a modern computerized spark control system, the amount of spark advance when the engine is operating normally is determined by...
Retarded
With ignition timing in this condition, some of the air-fuel mixture is pushed out of the cylinder before combustion is complete.
No airflow
With the engine idling at normal operating temperature, hold a finger over the diverter valve. What should you feel?
A hissing noise should be heard as air passes through the valve, and strong vacuum should be felt when a finger is placed over the valve inlet
With the engine idling, what should the technician observe when disconnecting the PCV valve?
The paper should be sucked against the opening
With the engine running at idle, remove the crankcase breather or oil filler cap. Loosely hold a piece of stiff paper over the opening. What should happen within 60 seconds if the PCV system is functioning properly?
Pulse width modulated EGR
With this type of EGR system, a solenoid opens and closes a vacuum valve about 30 times a second.
Positive backpressure EGR valve
With this type of EGR system, if there is little to no vacuum in the vacuum chamber, such as idle or WOT, or if there is little or no pressure in the exhaust manifold, the EGR valve will not open.
Negative backpressure EGR valve
With this type of EGR system, manifold vacuum combines with negative exhaust backpressure to close the vacuum bleed hole, and the EGR valve opens.
Negative backpressure EGR valve
With this type of EGR system, the diaphragm on the EGR valve has an internal vacuum bleed hole which is held closed by a small spring when there is no exhaust backpressure.
Pump and pulse air
What are the two basic types of air injection?
Diverter valve; one-way check valve
What are the two valves located in line between the air pump and the exhaust manifold?
Ignition timing
What determines whether the air-fuel mixture undergoes combustion at the right time?
Stores vapors when the engine is off, then when the engine is started, removes them from storage to burn in the engine
What does the EVAP system do with fuel vapors?
Routes crankcase gases to the intake system where they are drawn into the combustion chamber and burned
What does the PCV system do?
The vacuum level drops
What happens to manifold vacuum as engine speed increases?
Vacuum drops to zero
What happens to manifold vacuum at full throttle?
The high vacuum signal overcomes spring pressure to open the valve
What is the PCV valve's operating condition when the engine is at idle?
Spring pressure changes the valve opening to allow full flow
What is the operating condition of the PCV valve at cruise?
Spring pressure closes the PCV valve
What is the operating condition of the PCV valve during full throttle?
To continue the combustion process in the exhaust manifold, reducing emissions of unburnt fuel
What is the purpose of the air injection system?
To provide more oxygen to the catalytic converter and improve the oxidation of harmful pollutants
What is the purpose of the air injection system?
1-2 gallons
What is usually the capacity of the thermal expansion tank?
Fuel, oxygen, and heat
What three elements does the combustion process require?
Open and closed
What two types of PCV system have been used in the industry?
Ported vacuum and venturi vacuum
What two types of vacuum signal are used to operate the EGR valve?
Gasoline and diesel
What types of vehicles use EGR?
Coolant Temperature Sensor (CTS); Throttle Position Sensor (TPS); Mass Air Flow Sensor (MAF)
What typical basic computer inputs are needed to control the operation of a digital EGR valve?
Road draft tube
What was the first method used to vent crankcase vapors?
Older systems vented directly to atmosphere, contributing to air pollution
What was the main reason PCV systems were mandated on non-commercial vehicles?
Backfire
What will happen if fresh air is injected into a rich exhaust stream, like the exhaust created during rapid deceleration?
1973
What year were federal standards for NOx established?
Silencer
A pulse air injection system sometimes has this component added to muffle noise due to pressure pulsations.
Air pump
A pulse air system eliminates the need for...
Electric heating grid
A variety of approaches are used to heat the intake manifold, including:
Engine coolant
A variety of approaches are used to heat the intake manifold, including:
Exhaust gases
A variety of approaches are used to heat the intake manifold, including:
Fuel system air cleaner
Air entering the air injection pump can be filtered by:
Internal filtering device
Air entering the air injection pump can be filtered by:
Small auxiliary air cleaner
Air entering the air injection pump can be filtered by:
Normally closed
All EGR valves are of this type.
Malfunctioning vent line
Although all fuel filler caps used today are sealed, most of them are equipped with pressure/vacuum relief valves, which prevent damage in case of a...
Platinum and palladium
An oxidation catalyst (OC) contains which two precious metals as catalysts?
HC and CO
An oxidation catalyst reduces these two types of emissions.
Spring tension
As engine vacuum drops, what opens the PCV valve?
Closed
At WOT, venturi vacuum is the strongest, but manifold vacuum drops to very low levels. Therefore, the venturi control signal allows full manifold vacuum to the EGR valve, but because manifold vacuum is weak, the EGR valve is...
Low
At low engine speeds, vacuum at the carburetor venturi is...
Between 12,000 and 30,000 miles
At what intervals should PCV systems be checked?
Rich
Because cold air does not support good atomization of liquid fuel, cold engine startup requires the air-fuel mixture to be...
NOx
Because diesel engines depend on very high combustion temperatures and pressures, they are a source of...
Pressure could build and the fuel tank could explode; when temperatures fall and fuel vapor condenses, the fuel tank could collapse
Because fuel evaporates, what would happen if the fuel tank and carburetor float bowl were sealed?
20%
Before PCV systems were mandated, what percentage of vehicle emissions were from crankcase vapors?
500 degrees F
Before any catalytic converter can begin to reduce emissions, exhaust gas temperatures need to reach at least...
Vane pump
Belt-driven air injection pumps are normally a...
Atmosphere
Depending on the operating conditions of the air injection system, pressurized air may be injected into:
Catalytic converter
Depending on the operating conditions of the air injection system, pressurized air may be injected into:
Exhaust manifold
Depending on the operating conditions of the air injection system, pressurized air may be injected into:
Lean
Diesel engines tend to produce a lot of NOx at idle, when the air-fuel ratio is very...
Blow-by vapors
Dilution and contamination of engine oil, the formation of oil sludge, and pressure in the crankcase that could force oil past seals and gaskets are all problems caused by...
Yes
Do diesel engines use EGR?
No
Does the vane type air injection pump require periodic maintenance?
Rich
During engine warm-up, what kind of air-fuel mixture is required for smooth engine operation?
Pulled open by the increased vacuum signal
During light acceleration or cruise conditions, manifold vacuum increases and the EGR valve is...
1400 degrees F
During normal operation, the internal temperature of the catalytic converter will be about...
Engine speed should drop by 50 RPM or more
During testing of the PCV valve, what should happen to engine RPM when you pinch off the ventilation tube between the vacuum source and the PCV valve?
1968
Federal legislation was passed requiring closed PCV systems in what year?
Vacuum pump
For EGR operation on diesel engines, vacuum is provided by a...
Manifold heat
Fuel tends to condense when warm intake air-fuel mix hits a cold intake manifold wall. To reduce this tendency, either the manifold or the air in the manifold can be heated. This is called...
Off
Fuel vapors are stored in the canister when the engine is...
Vapor separator
Fuel vapors rise into this component through vent tubes. Liquid fuel and condensation are drained back into the tank while vapors escape through a vent line to the charcoal canister.
By diverting air away from the exhaust system during rapid deceleration
How does the diverter valve prevent backfires?
Vacuum overcoming spring tension
How is the EGR valve opened?
Redesigned fuel filler cap
One of the main components of the EVAP system is...
Blow them out with compressed air
If PCV hoses become dirty, you can...
Clean the old valve in solvent and make sure it rattles when shaken before reinstalling
If a PCV valve requires replacement, but a new valve is not available, you can...
Destroy the catalyst
If engine conditions resulted in excessive unburnt fuel being passed into the catalytic converter, temperatures in the converter could rise high enough to...
Rough running or stalling
If the EGR is activated at idle, during cold warm-up, or during WOT, what will happen?
NOx
If the temperature in the combustion chamber gets too high, this pollutant is formed.
Rhodium
In a TWC, this precious metal is used as a catalyst to reduce NOx.
Engine speed
In a belt-driven air injection system, the volume of air discharged by the pump changes with...
Through the air cleaner, carburetor, then into the engine
In a closed PCV system, excessive fumes are forced out the breather, then...
Aluminum oxide pellets or a ceramic monolith
In a conventional catalytic converter (oxidation catalyst), the catalyst is a coating on either of these two mediums.
Check valve
In a pulse air system, this valve performs the same function as in an air pump system - that is, to prevent exhaust gases from entering the air injection system.
Pressure relief valve
In a pump style air injection system, system pressure is controlled by...
5 psi
In a pump style air injection system, system pressure is normally under...
Inner air cavity
In an air injection system, the air pump consists of:
Pump housing
In an air injection system, the air pump consists of:
Rotor and vane assembly
In an air injection system, the air pump consists of:
Air pressure relief valve
In an air pump system, this valve may be built into the air pump housing.
Exhaust manifold
In an air pump type system, pressurized air is routed through pipes and hoses to an air injection rail or pipe, which is usually mounted on the...
Idle
In contrast to EGR valves on gasoline engines, EGR valves on diesel engines are fully open at...
Air injection system
In the event of air pump failure, exhaust gases could be forced up the air injection pipe and into the...
Exhaust gases
In the event that exhaust system pressure exceeds the air injection system pressure, what could be forced up into the air injection system?
1975
In this year, CA emissions regulations tightened to 0.9 grams per mile for HC and 9 grams per mile for CO.
1974
In this year, CA regulation required that HC and CO emissions not exceed 32 and 39 grams per mile, respectively.
Spark delay valve
In vacuum controlled spark advance systems, the purpose of this valve is to slow spark advance by delaying increasing vacuum signals to the advance unit.
Redesigned fuel tank
One of the main components of the EVAP system is...
Vapor separator
One of the main components of the EVAP system is...
Exhaust backpressure sensor
Initially, these sensors were separate from the EGR valve, and later were built into the EGR valve.
Orifice
Instead of a PCV valve, some engines use a carefully sized...
Vacuum diaphragm or electric solenoid
Most diverter/pressure relief valves are controlled with either...
1-2 psi
Most fuel filler cap relief valves allow air in freely but only allow air out if tank pressure is greater than...
Replaced; cleaned
Most manufacturers recommend that PCV valves be... rather than...
Fuel tank design and/or liquid check valves
Most modern systems have eliminated the vapor separator, and instead its function is served by:
Air delivery pipe(s)
Most pulse air systems include:
Check valve(s)
Most pulse air systems include:
Pulse valve(s)
Most pulse air systems include:
Using a redesigned main tank that allows 10-12% air space when the tank is full
Most systems solve the problem of fuel expansion by:
Port fuel injection
Most vehicles with this type of fuel delivery system are capable of controlling mixture without using intake air heating.
Applying vacuum with a handheld vacuum pump
Negative backpressure EGR valves are tested by...
The O2 sensor detects the high level of oxygen in the exhaust, which it interprets as a lean condition
On a vehicle with O2 sensors, what is accomplished by the use of air injection on cold startup?
The additional air allows for better converter operation while it is still below optimum operating temperature
On a vehicle with O2 sensors, what is accomplished by the use of air injection on cold startup?
The computer responds to the O2 sensor readings by commanding a richer air-fuel mixture, eliminating the need for a conventional choke mechanism
On a vehicle with O2 sensors, what is accomplished by the use of air injection on cold startup?
To lean out the rich air-fuel mixture entering the engine, avoiding a potential backfire
On an air injection system, what is accomplished by the gulp valve diverting air to the intake manifold on rapid deceleration?
Open
On diesel vehicles, what is the operating status of the EGR during idle?
Coolant temperature override (CTO) switch
On early computerized spark control systems, the purpose of this switch is to modify the vacuum control signal to the distributor to either improve cold drivability or reduce the temperature of an overheated engine.
Catalytic converter
On initial startup, some air injection systems also inject air into the...
Diverter valve
On some pump style air injection systems, the pressure relief function is built into the:
Pump housing
On some pump style air injection systems, the pressure relief function is built into the:
110 degrees F
On vehicles with O2 sensors, the thermal switch halts the operation of air injection once coolant temperature exceeds about...
High O2 content will fool the O2 sensor into thinking the air-fuel mix is too lean
On vehicles with O2 sensors, why can air injection not be used during normal engine operation?
Charcoal canister
One of the main components of the EVAP system is...
A stuck valve should be replaced; hoses should be cleaned
PCV systems are normally trouble-free, but they should be checked at intervals, and maintained in the following ways:
Manually pushing up the underside of the diaphragm
Positive backpressure EGR valves are tested by...
Valve spring
The EGR valve is held closed by what?
Stalling and rough idling
The PCV system should be checked whenever these signs of a ventilation problem occur:
Transmission switch or speed sensor
The electrical signal controlling the VSV can come from one of these two switches.
Air pump
The main components of a pump air injection system include:
Check valve
The main components of a pump air injection system include:
Diverter valve
The main components of a pump air injection system include:
Injection manifold(s) or pipe(s)
The main components of a pump air injection system include:
Cold engine startup
The thermostatic air cleaner operates only during...
Fuel bowl
The use of a fuel injection system is the most efficient way of controlling evaporative emissions because it eliminates the...
Temperature thermovalve
The use of this valve within an EGR system improves cold engine drivability.
Pulse air check valve
These valves are connected to the exhaust system, so that vacuum in the exhaust system pulls fresh air in, and exhaust pressure closes the valve.
Purge valve
This component is used to gain more control over the volume of canister fumes purged and purge timing.
Throttle positioner solenoid
This early method of preventing catalyst damage used a solenoid to hold the throttle plate open to a fast idle position (about 1500 RPM) when the throttle was quickly released, preventing the quick restriction of air that results in a rich mixture.
EGR
This emissions control system reroutes a small amount of exhaust gas into the intake cycle to dilute the intake charge, reducing combustion temperatures.
Catalytic converter
This emissions reduction device is installed in the exhaust system between the exhaust manifold and the muffler.
Injection manifold
This manifold, usually constructed of stainless steel tubing, includes a common air pipe with one injection nozzle to distribute pump air to each exhaust port.
Temperature thermovalve
This part is found in many EGR systems?
Vacuum amplifier
This part of the EGR system allows venturi vacuum to regulate the strength of the manifold vacuum signal to the EGR valve.
Thermal expansion tank
This tank is open to fuel at the bottom, with one or two small vents at the top.
Digital EGR
This type of EGR system controls EGR flow through orifices that are opened and closed by computer-controlled solenoids.
Air pump
This type of air injection system uses a belt-driven pump or an electric pump to pressurize air.
Oxidation catalyst (OC)
This type of catalytic converter only reduces emissions of HC and CO.
Three-way catalyst (TWC)
This type of catalytic converter reduces HC, CO, and NOx.
Ported vacuum
This vacuum signal comes from a port in the carburetor, located just above or below the throttle plate.
Venturi vacuum
This vacuum signal is highly sensitive to changing engine conditions, providing the most accurate source of EGR control.
Venturi vacuum
This vacuum signal provides the most accurate source of EGR control, but is too weak to operate the EGR valve.
One-way check valve
This valve allows air to flow freely into the exhaust manifold while preventing exhaust from flowing back into the air injection system.
Diverter valve
This valve prevents backfires during rapid deceleration.
1975
This was the first year that most vehicles sold were equipped with catalytic converters.
Thermal expansion tank
To prevent overflow in case of fuel expansion during high temperatures, some systems use a small auxiliary tank inside the main tank. This tank is called the...
Rich
Under deceleration, the closed throttle plates restrict air flow into the engine, resulting in an air-fuel mixture and exhaust stream that is...
Build up; drop
Under full-throttle conditions, crankcase pressures... while vacuum levels...
Intake manifold
Usually, EGR valves are mounted directly to the...
HC
Vacuum spark advance works to advance timing during deceleration. This helps avoid backfiring, and reduces emissions of...