Mitsubishi Lancer Evolution 7. Manual — part 238
ENGINE AND EMISSION CONTROL -
Emission Control System
17-13
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
GENERAL INFORMATION
The exhaust gas recirculation (EGR) system lowers
the nitrogen oxide (NOx) emission level. When the
air/fuel mixture combustion temperature is high,
a large quantity of nitrogen oxides (NOx) is
generated in the combustion chamber. Therefore,
this system recirculates part of emission gas from
the exhaust port of the cylinder head to the
combustion chamber through the intake manifold
to decrease the air/fuel mixture combustion
temperature, resulting in reduction of NOx.
The EGR flow rate is controlled by the EGR valve
so as not to decrease the driveability.
OPERATION
The EGR valve is being closed and does not
recirculate exhaust gases under one of the following
conditions. Otherwise, the EGR valve is opened
and recirculates exhaust gases.
D
The engine coolant temperature is low.
D
The engine is at idle.
D
The throttle valve is widely opened.
SYSTEM DIAGRAM
ON
Throttle body
EGR control
solenoid valve
Engine
control
relay
Battery
EGR valve
Crank angle sensor
Throttle position sensor
Engine-ECU
Engine coolant
temperature sensor
Air flow sensor
ENGINE AND EMISSION CONTROL -
Emission Control System
EGR control solenoid valve
Vacuum tank
Alternator
EGR valve
Throttle body
17-14
COMPONENT LOCATION
EXHAUST GAS RECIRCULATION (EGR)
CONTROL SYSTEM CHECK
1. Disconnect the vacuum hose (green stripe) from the EGR
control solenoid valve, and then connect a hand vacuum
pump via the three-way terminal.
2. When the engine is hot or cold, check the condition of
vacuum by racing the engine.
When engine is cold
(Engine coolant temperature: 20_C or less)
Throttle valve
Normal vacuum condition
Open quickly
No vacuum will generate
(the same as barometric pressure.)
When engine is hot
(Engine coolant temperature: 80_C or higher)
Throttle valve
Normal vacuum condition
Open quickly
It will momentarily rise over 13 kPa
3. Disconnect the three-way terminal.
4. Connect the hand vacuum pump to the vacuum hose
(green stripe).
5. Check whether the engine stalls or the idling is unstable
when a vacuum of 27 kPa or higher is applied during
idling.
Three-way
terminal
EGR control
solenoid valve
Vacuum
tank
Alternator
EGR control
solenoid valve
Vacuum
tank
Alternator
Green stripe
ENGINE AND EMISSION CONTROL -
Emission Control System
17-15
EGR VALVE CHECK
1. Remove the EGR valve and inspect for sticking, carbon
deposits, etc. If found, clean with a suitable solvent so
that the valve seats correctly.
2. Connect a hand vacuum pump to the EGR valve.
3. Apply 67 kPa of vacuum, and check that the vacuum
is maintained.
4. Apply a vacuum and check the passage of air by blowing
through one side of the EGR passage.
Vacuum
Passage of air
5.3 kPa or less
Air is not blown out
27 kPa or more
Air is blown out
5. Replace the gasket, and tighten to the specified torque.
Tightening torque: 20 ± 2 N·m
EGR PORT VACUUM CHECK
1. Disconnect the vacuum hose (White stripe) from the
throttle body EGR vacuum nipple and connect a hand
vacuum pump to the nipple.
2. Start the engine and check vacuum remains fairly constant
after racing the engine.
NOTE
If the vacuum fluctuates, the throttle body EGR port may
be clogged and need cleaning.
White stripe
Throttle body
Vacu-
um
Engine speed (r/min)
ENGINE AND EMISSION CONTROL -
Emission Control System
17-16
EGR CONTROL SOLENOID VALVE CHECK
NOTE
When disconnecting the vacuum hose, always make a mark
so that it can be reconnected at original position.
1. Disconnect the vacuum hose (yellow stripe, green stripe,
white stripe) from the solenoid valve.
2. Disconnect the harness connector.
3. Connect a hand vacuum pump to the nipple to which
the green-striped vacuum hose was connected.
4. Check airtightness by applying a vacuum with voltage
applied directly from the battery to the EGR control
solenoid valve and without applying voltage.
Battery voltage
B nipple condition
Normal condition
Not applied
Open
Vacuum maintained
Applied
Open
Vacuum leaks
Closed
Vacuum maintained
5. Measure the resistance between the terminals of the
solenoid valve.
Standard value: 29 - 35 Ω (at 20_C)
Battery
A
B
C
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