1990 MITSUBISHI ECLIPSE Service Manual

EMISSION CONTROL SYSTEMS - General Information25-3
INon-Turbo for California
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oxz pJCatalytic converterEGR temperature sensor
ON Purge control
solenoid
valve
EGR controlsolenoid valve
Turbo for FederalAir
cleper
E
-II 11-l I-d-h I
-u’Catalytic a3nverter
in
Purge controlsolenoid
valve
6EM0260

EMISSION CONTROL SYSTEMS - General Information
Turbo for CaliforniaAir
sokkoidvalvePurge control
I/ I
, ,LUII‘P
p injector
Catalytic converter
EGR temperaturesensor
t
EGR controlsolenoid valve

‘Sv’_ -EMISSION CONTROL SYSTEMS
-Exhaust Gas Recirculation (EGR) System25-5
FYHAUST GAS RECIRCULATION
\ ,GR) SYSTEM
RZSCAAB
EGR system is designed to reduce oxides of
nitrogen in exhaust emissions. In this system, the
exhaust gas is partially recirculated from the
ex-haust manifold into the intake manifold while EGR
flow is controlled by the
EGR control valve.
OPERATION
The amount of
EGR flow is reaulated bv the throttlevacuum is low during engine idling, or during
wide-open throttle operation, the EGR control valve
is closed by the force.of the spring, with the result
that there is no flow of EGR gas.
If the temperature of the engine coolant is below
65°C (149”F), the therm0 valve opens and the “E”
port vacuum is leaked to the throttle body “A” port,
with the result that the
EGR valve does not function.
l ’E”Portvacuum. &cause the “E” port
Therm0 valve
NOTE-This figure shows Non-Turbo.6EM0136

-.-
25-6EMISSION CONTROL SYSTEMS- Exhaust Gas Recirculation (EGR) System
OPERATION
The engine control unit functions to calculate the
engine load, based upon the intake air volume
signals (from the air-flow sensor) and the rpm
signals (from the crank-angle sensor), and the
EGRcontrol solenoid valve is activated according to the
engine load. The
EGR amount is then regulated
according to the engine load calculated in this way.maintaining driveability during cold.
When, as a result of clogging of the
EGR cant’valve or as a result of an operational
malfunctio,.,the
EGR flow volume decreases, the EGR gas
temperature downstream. from the
EGR control
valve decreases. The engine control unit functions
to detect the
operation conditions of the EGRLoad
a Intake air volume/Engine rpmsystem by this characteristic.
If, however, the engine coolant temperature is low,
the actuation duty is attenuated, the
EGR control
valve activation negative pressure (vacuum) is
leaked from the throttle body A port, thus reducing
or interrupting the
EGR flow volume and therebyThe temperature of the
EGR gas is detected by the
EGR gas temperature sensor which is equipped at
the
EGR control valve; when the temperature
decreases to a low level, the engine warning light
(malfunction indicator light) illuminates in order to
advise the driver that a malfunction has occurred in
the
EGR system.
EGR
contcEGR control
solenoid valve
/Control
relay
1Engine control unit
Enginewarning
light

EMISSION CONTROL SYSTEMS - Exhaust Car Recirculation (EGR) System25-7Duty ratio
I .,
ON e-_-m-L--l
T2L1.TlOFF---
m
1c1-i1e2100260 msec. 60 msec.
EGR CONTROL VALVE
Spring
NOTEThe duty ratio is the ON duration ratio of 16.7 Hz pulse or
T2/T1.The higher the duty ratio, the more mean current flows to the
boost meter. and as a result, the boost meter reads the higher
value.The smaller is the duty ratio, the boost meter reads the smaller
value.
Diapl
.Valveiragm
To Intakemanifold
Exhaust gasApply vacuum
7EM0012
NOTEThis illustration indicates Non-Turbo models.7EMOO15The EGR control valve is a diaphragm that functions
to control the flow of
EGR gases by opening and
closing the valve according to the negative pressure
(vacuum) acting upon the partitioned chamber.When the negative pressure becomes stronger than
the spring force, the valve opens, as shown in the
illustration, and the exhaust gases can flow.
Valve
BlmetzII
17EMOO16
THERM0 VALVE
The therm0 valve functions in response to the temperature of
the engine coolant. thus controlling the negative pressure
acting upon the
EGR control valve.
The valve opens at a temperature of
65°C (149°F) or lower, and
closes at
65°C (149°F) or higher.

25-8EMISSION CONTROL SYSTEMS- Exhaust Gas Recirculation (EGR) System
EGR TEMPERATURE SENSOR
_Sensor part
/
/-
/* * Conneyor,
lEM0033Enaine control unit
EGR temperature sensor
Kf+
--
6EY0208--\EGR temperature sensor is thermistor type. It
detects the temperature of gas passage in EGR
control valve, converts the detected temperatureto electric signal and sends the signal to the engine
control unit.
To EGR control
+I thl
.ottleControl relay
solenoid valve
h
LBattery
g
0s
l$ine control5FW532EGR CONTROL. SOLENOID VALVE
The
EGR control solenoid valve is the duty-control type of
solenoid valve; it functions to regulate the EGR control valve
activation negative pressure (vacuum).
7

---- .~ _ _EMISSION CONTROL SYSTEMS
- Catalytic Converter I Air-fuel Mixture Ratio Control System25-9
,ATALYTlC CONVERTERRZXIAAAThe catalytic converter is installed on the middle ofand surrounded by a stainless steel shell.
the exhaust pipe under the floor.The catalytic converter oxidizes carbon monoxide
This catalytic converter uses a monolithic type
catalyst with a honeycomb structure that has itsand hydrocarbon, and reduces oxides of nitrogen.
surface coated with catalytic components. Thewhich are present in the exhaust gas, in order to
minimize their emission levels.
catalyst is supported by a stainless steel wire mesh
Exhaust air
3Stainlesssteei shell
\CoverStainless steel wire mesh
lEM0031
AIR-FUEL MIXTURE RATIO CONTROL
SYSTEMThe
MPI system is a system which employs the signals from
the oxygen sensor to activate and control the injector installed
at the each cylinder head thus precisely regulating the air-fuel
mixture ratio and reducing emissions,
This in turn allows the engine to produce exhaust gases of the
proper composition to permit the use of a three-way catalytic
converter. The three-way catalytic converter is designed to
convert the three pollutants
(1) hydrocarbons (HC), (2) carbon
monoxide (CO), and
(3) oxides of Nitrogen (NOx) into harmiess
substances.There are two operating modes in the
MPI system:
(1) Open Loop
Air-fuel ratio is controlled by information programmed into
the engine control unit at manufacture.
(2) Closed Loop
Air-fuel ratio is varied by the engine control unit based on
information supplied by the oxygen sensor.
NOTEFor detailed information concerning the
MPI system, refer
to Fuel System.

25-10EMISSION CONTROL SYSTEMS - Crankcase Ventilation Svstem-
CRANKCASE VENTILATION SYS-fUSFAAA,r
TEMA closed-type crankcase ventilation system is
uti-with blow-by gases, and this mixture passes
lized to prevent the blow-by gas from escaping into
through the PCV valve into the intake manifold.
the atmosphere.The PCV valve has a metered orifice through which
This system has a positive crankcase ventilation
the mixture of fresh air and blow-by gases is drawn
valve
(PCV valve) at the rocker cover. This system
into the intake manifold in response to the intake
supplies fresh air to the crankcase through the air
manifold vacuum. The valve capacity is adequate forcleaner. Inside the crankcase, the fresh air is mixed
all normal driving conditions.
From air cleanerPositive crankcaseventilation valve
a Blow-by gas
a Freshair
To intakemanifold
6EM0115
SiringPlunger
7EMOOZi