Emissions Control Systems and Components

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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?

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?

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...

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.

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?

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.

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...

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?

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:

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.

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.

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.

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:

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...

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.

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...

1969

Closed PCV systems were required as of what vehicle model year?

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...

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...

Redesigned fuel filler cap

One of the main components of the EVAP system is...

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...

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...

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...

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:

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.

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...

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...

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?

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.


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