1990 MITSUBISHI ECLIPSE coolant temperature

FUEL SYSTEM- Intake Air Control
SPECIFICATIONS
ternsThrottle body
Throttle bore diametermm
(in.1Fast idle air valve
TwValve closing temperature
“C (“F)
Idle speed control servo
TypeSpecifications
60 (2.362)
WAX type
Approximately 50
(122)Stepper motor type
FAST IDLE AIR VALVEEngine coolant
LAir valve
Waxpellet
Valve seat
6FUO642The fast idle air valve is a wax actuated valve. The
engine coolant circulates around the wax pellet.
causing the air valve to be forced out as the coolant
temperature increases, thus decreasing the bypassair flow rate. The valve is closed completely when
the coolant temperature is approximately 50°C
(122°F) or higher.

14-14
.._~- ---.FUEL SYSTEM
- Sensors
SENSORSRlUGENERAL DESCRIPTION
The types and functions of the sensors are as listedsend corresponding signals to the engine control
below. These sensors detect engine conditions and
unit.
SENSORSFUNCTION
AIR FLOW SENSOR
fSenses the intake arr volume with a Karman vortex flow meter.
INTAKE AIR TEMPERATURE
SENSORSenses the Intake air temperature (temperature of air at
the point of entry into the air cleaner).I
BAROMETRIC PRESSURE
SENSORISenses the barometric pressure faltrtude) wrth a
semiconductor diffusion type pressure sensor.
$;;OOf;T TEMPERATURESenses the engine coolant tern
THROTTLE
POSITISenses the throttle
tI
IDLE POSITION SWITCHSenses whether or not the accelerator pedal is being
operated with a contact switch.
Senses the top dead center on compression stroke of
NO. 1 and No. 4 cylinders with an LED and photo diode pair.
CRANK ANGLE SENSORSenses the crank angle of each cylinder with an LED
and photo diodepair.
T
OXYGEN SENSORSenses
actrvation of the air con
POWER STEERING OIL
PRESSURE SWITCHc-lSenses the power steering ‘load with a contact switch.
IGNITION SWITCHSenses ON/OFF
posrtion of the ignition switch.I
Senses engine cranking.
,
IGNITION TIMING
ADJUSTMENT TERMINALWhen this terminal is shorted, the ignition timing and idle
speed control servo is set in the adjustrng mode by the enginecontrol unit.
INHIBITOR SWITCHSenses the *P” and “N” positthe automatic transaxle.Senses.
by pieto-electric element,. cylinder block
vibrations that occur when there ISengineknocking.
CONTROL RELAY
(Fuel pump drive signal)
lFnorne ianitron sianal!Senses ignrtton coil prIman/ voltage.

14-18FUEL SYSTEM - Sensors
tBAROMETRIC PRESSURE SENSOR
Barometnc rxessure sensor
EC1537
Barometncpressure sensor
Enginecontrol unit
1OFUO576
/
760 (30)Barometric pressure mmHg
(in.Hg)EC1551A barometric pressure sensor is
alas mounted on
the
aif flow sensor. It senses the barometric
pressure and converts it to electrical voltage which
is sent as a signal to the engine control unit.
Using this signal, the engine control unit calculates
the altitude
of.the location where the vehicle is, and
corrects the fuel injection quantity for the optimum
air-fuel ratio at that altitude, and also corrects the
COOLANT TEMPERATURE SENSOR
Terminal 26EL0069ignition timing.
This ensures improved driveability at high altitudes.
The barometric pressure sensor converts the pres-
sure to a voltage making use of the fact that the
resistance of a strain gauge changes in direct
proportion to the pressure as shown in this diagram
which
illustratestherelationship between
barometric pressure and output voltage.
Engine control unit
Coolanttemperature
sensor
-a
Tg-I
h-esI
*
5 volts
LizIdr
tSFUOLSL
L0 (32120 (68)Coolant temperature -The engine coolant temperature sensor installed in
the coolant passage of the thermostat case is a
thermistor whose resistance changes with the
engine coolant temperature.
The
annine control unit iudoes the enoine warm UDstate based on the output voltage of this sensor and
provides optimum mixture enrichment when the
engine is cold.
The sensor characteristics are as shown above..:I

‘7JFUEL SYSTEM
- Sensors14-23AIR CONDITIONER SWITCH
Batten/
-31 .,Air conditioner unitlSAO735‘Air conditioner
control unitI”.._. ,voltage
Dual pressureswitch
-f@ -//Q.j
/
Coolanttemperature6FU1148
switch
Engine control unit
3Air conditioner
This switch sends the air conditioner ON/OFF signal
to the engine control unit.
When the air conditioner is turned on and the enginecontrol unit receives the ON
signal from the switch,
it commands the idle speed control servo
toincrease the idle speed to the preset rpm. Thus
engine rpm loss due to air conditioner operation
while the engine is idling is prevented and smooth
idling operation is ensured.

FUEL SYSTEM- Engine Control Unit14-29
SFUllSOTerminal
ConnectionTerminalConnectionNo.
No.
1Self-diagnosis output53EGR control solenoid valve (California only)
2Diagnosis/data transfer select terminal54Power transrstor for No. 1 and No. 4 cylinder
‘3Turbo meter
55Power transistor for No. 2 and No. 3 cylinder
4Oxygen sensor56Control relay (Fuel pump control)
5Power steering oil pressure switchl 57Fuel-pressure control valve
6Idle position switch58Coil “Al ” for idle speed control servo
7Air conditioner switch59Coil “A2” for idle speed control servo
8Intake air temperature sensor60No. 3 injector
l 9Detonation sensor61No. 4 injector
10Air flow sensor62Purge control solenoid valve11
-63Control relay
12Ignition timing adjustment connector64Engine warning irght (Malfunction indicator light)
13Control relay (Fuel pump drive signal)65Air conditioner relay
l 14Air flow sensor active filter reset66Control relay
15EGR temperature sensor (California only)67Coil “Bl ” for idle speed control servo
16Barometric pressure sensor68Coil “B2” for idle speed control servo
17Sensors ground101Ground
18Vehicle speed sensor102Power supply
19Throttle position sensor103Power supply for backup
20Coolant temperature sensor
104Inhibitor switch
21Crank angle sensor‘105
Waste gate solenoid valve
22Top dead center sensor106Ground
23Power supply for sensors (5 volts)107Power supply
24Sensors ground108“ST” terminal for ignition switch
51No. 1 injector109Ignition pulse detect
52No. 2 injector170“IG ” terminal for ignition switch
NOTETerminals indicated by the l symbol are applicable only to turbo models.

14-30SELF-DIAGNOSISFUEL SYSTEM- Engine Control Unit
There are 16 diagnosis items, as listed below; the
diagnosis results are stored in computer memory.The diagnosis memory is maintained by backup
The stored results can be ready by connecting apower from the battery (not by way of the ignition
circuit tester or voltmeter to the diagnosis
connec-switch) so that it will not be lost even if the ignition
switch is turned OFF.
tor.
DiagnosisOutput pattern
codeEl
None
lP
@ 11l-l
@ 12n@ 13
@ 14
@ 21Ul n
Diagnosis items
Faulty computer in the engine control unitMalfunction of the air/fuel ratio control system
Open or short circuit in the oxygen sensor circuit
Open or short circuit in the air flow sensor circuit
Open or short circuit in the intake air temperature sensor
circuit
Open or short circuit in the throttle position sensor circuit
Open or short circuit in the engine coolant temperature sensor
circuit
022u1 nn
No voltage change of the crank angle sensor signal
,
@
23
u u-inn
No voltage change of the TDC sensor signal
24uu-uvinnnnNo voltage change of the vehicle speed sensor signal
Q25uuuuuunnnnnOpen or short circuit in the barometric pressure sensor
2 31I-~-~---~ nOpen circuit in the detonation sensor circuit
@ 41uuul nOpen circuit in the injection circuit
042UUuLJul
Malfunction of the control relayOpen or short circuit in the fuel pump drive circuit
z 43UUULnlulMalfunction of the
EGR system
Open or short circuit in the EGR temperature sensor circuit
%4u u u uvinnOpen circuit in either of ignition coil circuit
0nNormal (with none of above faults)
. IA-r-NUltl 1: l 2: for California@ denotes items indicated by an illuminated engine warning light

__.-~-..- -
FUEL SYSTEM- Ermine Control Unit
FAIL-SAFE AND BACKUP FUNCTiON
(1) The fail-safe function controls the system so
that passenger and vehicle safety can be
maxi-
mized. in the event of failure of sens.ors or other
parts.If a sensor related to
ISC fails, for example, the
engine control unit is programmed to prevent
sharp increases in the engine speed.(2) The backup function of the engine control unit
ignores the output signal of a failed sensor and
instead uses a built-in program or set of values
so that the vehicle may continue to function. The
operating state when the backup function is
being used, is termed the emergency mode, and
the engine, control unit keeps the engine warn-
ing light ON during this mode.
Fail-safe/Backup Function
Control contentsFaulty system
Fuel injection control
Idle speed controlIgnition timing control
Air flow sensor
Uses throttle position sensorFixes stepper motor atUses throttle position sensorsignal for control.
position wider than idle.signal for control.
Intake air
temper-Provides control with intake
Provides control with intakeProvides control with intake
ature sensorair temperature assumed to
be 25°C (77°F).air temperature assumed toair temperature assumed tobe 25°C (77°F).be 25°C (77°F).Throttle position
-Does not perform driving and-sensor
acceleration/deceleration
control.
Engine coolantProvides control with engine
Provides control with engineProvides control with engine
temperaturecoolant temperature
coolant temperaturecoolant temperature
sensorassumed to be 80°C (176°F)assumed to be 80°C (176°F).assumed to be 80°C (176°F).BarometricProvides control with
baro-Provides control with baro-Provides control with baro-pressure sensormetric pressure assumed to
be 760
mmHg (30 in.HgI.metric pressure assumed tometric pressure assumed tobe 760 mmHg (30 in.Hg).be 760 mmHg (30 in.Hg).Detonation sensor
-Retarded about 3 degree.Ignition coil
Fuel not injection to a cylinder-whose ignition signal is
abnormal.
TDC sensorOxygen sensor
No fuel injection.-
Feedback control of air/fuel-
ratio by oxygen sensor signal
is not made.

FUEL SYSTEM- Fuel Injection Control14-33
FUEL INJECTI& CONTROLGENERAL DESCRIPTION
Air flow sensor
cBarometric Dressure sensor
Coolant
temr3erature sensorITop dead center sensor
ignition switch
-
c
6FUO569The engine control unit activates the injectors andFuel is injected into each cylinder sequentially, and
controls the fuel injection rate in response. to thetakes place once for each cylinder every two
sensor information so that the optimum
air/fuel ratiorevolutions of the crankshaft. The injection duration
can be maintained at all times under ever-changing(namely the injector activation time) is the basic
engine operating conditions. The fuel injection rateactivation time determined according to the intake
is determined by the injection frequency corres-air volume of each cylinder, with corrections applied
ponding to the engine speed, and by the injectionaccording to the intake air temperature, engine
duration corresponding to the intake air volume.coolant temperature and other factors.