ignition MITSUBISHI ECLIPSE 1990 Owner's Guide

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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.

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14-44FUEL SYSTEM- Idle Speed Control
IDLE SPEED CONTROL
RlUU*I,GENERAL DESCRIPTION
If the load changes while idling, the idle speed
control servo is activated according to the preset
control logic to control the air flow that bypasses thethrottle valve, thus maintaining the optimum idle
speed.Fast idle air valve
Idle speed
control servo
Cooiar
To intakemanifoldFrom air
cleanerSpeed
adjustrng screwInhibitor switch
Ignition switch
Coolant temperature sensorThrottle position sensor
Crank angle sensorVehicle speed sensor
Air conditioner switch
Barometric pressure sensor
Power steering oil
pressure switch
Intake air te.mperature sensorIdle position switchIgnition timing adjustment
terminalSelfdiagnosisIdata trans-
mission switching terminal
6FUO796
Input signal reading
-3I9Control modedecision
II
41*
Target speed dataIdle speed control---cIdle speed
feedback controlservo position- Target position data
control
Idle speed controlIdle speed control
servo dnve pulse-Drive pulse setting
Drive pulse setting-servo drive pulse
setting data

FUEL SYSTEM -Idle Speed Control14-49
Servo ControlServo control includes feedback control and position
ontrol. In feedback control, the engine control uniti;onstantly calculates the actual idle speed, and if
the
value differs from the target idle speed, the unit
drives the stepper motor to adjust actual speed to
Feedback ControlWhile the engine runs at idle speed, the stepper
motor is activated to keep the engine speed at the
preset target idle speed by controlling the bypass air
volume.
The target idle speed that is optimum for each
operating condition (including air conditioner switch
ON/OFF) has been preset. This engine speed
feedback control is provided under stabilized idling
conditions and not when any of the following
conditions occur.
l When the vehicle is moving at 2.5 km/h (1.6
mph) or more.the target value. In position control, the idle speed
control
is adjusted to the target position to cope
with air conditioner and other load changes. Position
control is also performed when cranking the engine
and decelerating.
lWhen the idle switch is turned from OFF to ON,
and while the idle switch is in the OFF position.
lWhen the air conditioner switch is turned from
ON to OFF, or vice versa.
l When power steering oil pressure switch is
turned from ON to OFF, or vice versa.
l When the ignition switch is turned from ST to
IG, or vice versa.
l While the dash pot control is in operation.
lWhen the inhibitor switch is switched from “N”
range to “D” range or vice versa.
If-1Air conditioner switch
Idle speed
control servo
r------ -- -‘,
(N range)4* I-I
BI
8
IL -L
- !5ysr motor 1I
zIdle upIStepper motor 7Engine
PII2. I.1Coolant temperature
tL.---m--v--JJ
Engine speed
I6Fuo6oo
Servo Drive Steps
(1) If there is a difference between the target and actual idle
speeds, the servo is activated the number of angular steps
corresponding to the difference, thereby extending or
.retracting the pintle to control the amount of bypass air, and
adjusts the actual idle speed to the target value.
Difference between the target
and actual idle speed fpm6FUO699I
Time sec.
c
6FUO76!The sewo drive steps during idle speed feedback Control
van/ as shown at the left.

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14-52FUEL SYSTEM - Idle Speed Control
4
Start of deceleration
DLhq ON
position
I*2 to 6
Time sec.6FUO295
II)
0(32180(176)Temperature “C 1°F)6FUO29t
CONTROL WHEN THE ENGINE SPEED IS UNUSUALLY LOWThe followi
gcontrols are provided when the engine speecfalls below
i5;D rpm after the engine has been fully warmed-up
[with engine coolant temperature more than
55°C (131”F)].
(1) During feedback control
The idle speed control servo is activated immediately by a
particular number of angular steps which represent the
feedback correction.
(2) During servo position control
The idle speed control servo is activated to conform to
aposition corresponding to an increased number of steps
(46
steps).DASH POT CONTROL
Control is provided to dampen the extending motion of the
pintle from a certain opening degree, thereby absorbing
deceleration shocks.
(1) Control while cruising
While cruising or racing, the idle speed control servo is
activated to further open the bypass air path corresponding
to the dash pot position which is more open than the idle
position.The idle speed control servo is activated in this way when
the following conditions are met.
l Engine speed 500 rpm or higher
l Idle position switch in the OFF position
The dash pot position is dependent on the throttle valve
opening map value.,
(2) Control during deceleration
When the vehicle is decelerated from a cruising or racing
speed, the idle speed control servo is activated to close the
bypass air path gradually from the dash pot position so that
the intake air volume is not abruptly reduced, thereby
dampening deceleration shocks.
The idle speed control servo is activated when either one of
the following conditions are met.
lWhen the throttle position sensor output voltage drops
l When the idle switch is turned on.
CONTROL WHEN STARTING
While the engine is being cranked, the idle speed control servo
is controlled to provide optimum bypass air volume for starting.
Immediately after the ignition switch is turned on, idle speed
servo position control is provided to achieve the optimum
_
position.

FUEL SYSTEM -Idle Speed Control I Power Supply Control14-53
IIEngine has started.(1) Idling stabilization control immediately after starting
Immediately after starting, the idle speed control servo
sactivation steps are increased above the idle position; in.-
‘Bother words, bypass air volume is increased. The numberof steps are decreased gradually afterwards. The increased
55number of steps are preset as a map value according to theP2f/-/ engine coolant temperature.
Idle servo position
I
Time sec.
c
6FUO756
6FUO29z
!DLE STABILIZING CONTROL AT HIGH TERPERATURE
If the engine coolant temperature exceeds
&k (194°F) when
the engine is started, the feedback target speed after the
engine has started is increased a set value which is higher thannormal and then is gradually decreased.
CONTROL DURING IDLE SPEED ADJUSTMEN?
Grounding the ignition timing adjusting terminal and diagnosis/
data transfer select terminal causes the idle speed control
servo to be fixed at a position corresponding to the idle position
after warm-up. Idle speed is therefore adjusted with the servo
at the preset position after warm-up (9 steps).
The altitude compensation control is applied to thisposition,
meaning that the motor shifts to a position so that the pintle is
further retracted at high altitudes.
POWER SUPPLY CONTROL
GENERAL DESCRIPTION
RlUAAA
7FUO51

FUEL SYSTEM- Power Supply Control
Battery
L11The engine control unit controls the power
suv ’tcthe sensors, engine control unit and
actuate,A;the control relay.
-P
.
-p.Ignition switch
Inn yr
To air flow sensor,crank angle sensor,idle speed controlsetvo. injectors
Control relay
Relay controlFuel pump
controlIgnitionswitch signal
Enginecontrol
unit
I6FUOl’
Power Supply ControlWhen the ignition switch on signal is input, the
engine control unit energizes the control relay coil
L3to turn on the
S2 switch, thus supplying power to the
injectors, air flow sensor, idle speed control servo,
Fuel Pump ControlWhen cranking the’engine (ignition switch at the ST
position), the engine control unit energizes the
Lcoil to turn on the
S switch, thus activating the fuel
pump.While operating the engine (ignition switch at the
IGposition), the crank angle sensor signal is input to
the engine control unit, which energizes the
L,
etc.Approximately seven seconds after input of
theignition switch off signal, the unit turns off the
Sswitch.
control relay coil to keep the
SI switch on, thus
continuing to activate the fuel pump.
When the crank angle sensor signal fails to be
inputfor 0.6 second or longer due to engine stalling,
.,the engine control unit immediately turns
thz. 5switch off to stop the fuel pump as a safet)
precaution.

F
FUEL SYSTEM -Auto-cruise Control System'l4-61
AUTOCRUISE CONTROL UNIT
Je auto-cruise control unit incorporates a micro-computer which provides the set coast, resume,
acceleration, cancel, low-speed limitation,
high-speed limitation, overdrive OFF control, and
auto-
matic cancellation functions. The microcomputer
inputs signals from the vehicle speed sensor and
the switches, and outputs Control signals to the
actuator’s DC motor, the electromagnetic clutch,and the automatic
.transaxle (4 A/T) control unit in
accordance with the programming (software) of themicrocomputer.
CONTROL LOGIC BLOCK DIAGRAM
--
Auto-cruise control UnitIgnitionswitcha.-.
I
Input interface circuit
piz7q.f~~
I
L
Micro-
computer
jutput interface circuitIr--lI----
--7I IActuatorI
Electromagnetic
clutch coil
OD-OFF out-
put circuit
NC: Normally closed

FUEL SYSTEM - Auto-cruise Control System14-63
FixedDecebFixed
speed -bb-Highration+ c- speed
Vehicle
speedLow
SET ON
switch
OFF
DC StoPmotor Decele-
ration(RELEASE)07LOcaWhen the SET (COAST) Switch
,is Held Down
While the SET switch is ON, the actuator’s DC motor is caused
to rotate to the
RELEASE side; the vehicle speed when the
switch is switched
OFF as deceleration continues is entered in
the memory, and is thereafter controlled as the fixed speed.
Note that the vehicle speed must be the low-speed limit
[approximately 40 km/h (25 mph)] or higher.
Vehicle speed
Cancel signalElectromagnetic
clutch
RESUME switchRESUME (ACCEL) SWITCH
When the RESUME (ACCEL) Switch is Turned after the
Auto-cruise Control has been Canceled
When (after the auto-cruise control system is canceled by the
cancel signal) the RESUME switch is switched from OFF to ON
while driving at a vehicle speed which is the low-speed limit
[approximately 40 km/h (25 mph)] or higher, the vehicle speed
memorized before cancellation of the auto-cruise control
system will be controlled as the fixed speed.
Even if the vehicle speed is at or below the low-speed limit,
there can be a return
to: the set speed (before cancellation of
the auto-cruise control system) by using the accelerator to
increase the vehicle speed to 40 km/h (25 mph) or higher and
then switching the RESUME switch from OFF to ON.
Note that
jhe set speed (before cancellation of the auto-cruise
control system) will be erased from the memory circuit of the
control unit if the MAIN switch or ignition switch is switched
from ON to OFF or the vehicle speed is decreased to 35 km/h
(22 mph) or less, and thereafter the auto-cruise control system
will not operate even if the RESUME switch is turned ON.
HighLow
18pprOX.40 knVh(25 mph) or lugharl
ON
OFFI
ON
OFF
ON
OFF1IActuatorAcceleration
(DC motor)(Pff LL) Stop
RESUME (reset)Fixed-speed control
Autocruise control system cancellation07LOOO5

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14-68FUEL SYSTEM - Auto-cruise Control System
ACCELERATOR PEDAL SWITCH OFF FUNCTION
The accelerator pedal switch senses the operating
condition of the accelerator pedal.
This function turns OFF the accelerator pedal switchin the auto-cruise control mode during which the
accelerator pedal is
inoperative (accelerator pedal
switch ON).In the auto-cruise control mode, the control
UP;+microcomputer outputs an ON signal (HIGH)
c,stantly, causing transistor
Tr, to be turned ON.
At this time, transistor
Tr2 turns OFF, causing ON
signal I from
.the A/r control unit to be shut off,
which results in the accelerator pedal switch being
turned OFF.
Ignition switch IG7
Ancontrol unitn-l
‘.
INot in operation 1 OFF 1 ON 1Accelerator
pedal switch
(depressed: OFF)uto-cruise control
unit
V
Cruise control ON
Cruise control OFF
mm&m07AoQ10