1991 MITSUBISHI 3000GT engine

SERVICE ADJUSTMENT PROCEDURES
MlBFHSU
BASIC IDLE SPEED ADJUSTMENT
NOTE(1) The basic idle speed has been factory-adjusted with the
speed adjusting screw (SAS) and does not normally require
adjustment.(2) If the adjustment is required, first check that the ignition
plug, injector,
ISC servo, and compression pressure are
normal.
(1) Before starting the inspection and adjustment procedures,set the vehicle in the following conditions:
l
Engine coolant temperature: 80 to 95°C (176 to 205°F)l Lights, electric cooling fan, accessories: OFF
lTransaxle: Neutral (P range on vehicles with automatic
transaxle)l Steering wheel: Straightforward position
(2) When using the multi-use tester, connect it to the diagnosis
connector.
NOTEThe connection of the multi-use tester grounds the
self-
diagnosis/data transmission selector terminal.
(3) When not using the multi-use tester, proceed as follows:
@) Insert a paper clip into the l-pin blue connector as
shown in the illustration. FUEL SYSTEM
- Service Adjustment Procedurks13-31
i
@ Connect a primary-voltage-detecting tachometer to the
paper clip.
NOTEThe
tacho/neter should read l/3 of the actual engine
speed. This means that the actual engine speed is thetachometer reading multiplied by 3.
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13-32FUEL SYSTEM - Service Adjustment Procedures
@ Using a jumper wire, ground the self-diagnosis/data
transmission selector terminal (terminal
@) of theI
diagnosis connector (white).
dSelf-diagnosis/
ydata transmission
(4) Remove the waterproof female connector from the ignition
timing adjusting connector (brawn).(5) Using a jumper wire, ground the ignition timing adjusting
terminal.(6) Start the engine and run at idle.
(7) Check the basic idle speed.
When using the multi-use tester, select item No. 38 and
read the idle speed.
Basic idle
speeci: 700 + 50 rpm
NOTE(I) The engine speed may be low by 20 to 100 rpm while
the vehicle is new [distance driven approx. 500 km (300miles) or less], but no adjustment is necessary.
(2) If the engine stalls or speed is low despite a sufficient
distance driven [approx. 500 km (300 miles) or more], it
is probably due to deposits on the throttle valve. In thiscase, clean the throttle valve. (Refer to
P.13-33.)(8) If the basic idle speed is out of specification, adjust by
turning the speed adjusting screw (SAS).
NOTE
If the idle speed is higher than the standard value even with
SAS fully tightened, check to see if there is evidence of theidle switch (fixed SAS) being moved. If the idle switch
seems to have been moved, adjust it. If it does not seem tohave been moved, there may be a leak caused by
deteriorated fast idle air valve (FIAV). In such a case, replacethe throttle body.
(9) Turn the ignition switch OFF.
(lO)When the multi-use tester has not been used, remove thejumper wire from the self-diagnosis/data transmission
selector terminal.
(11)Remove the jumper wire from. the ignition timing adjustingterminal and replace the connector back again.
(12)Start the engine again and run at idle for
10 minutes to
make sure that the engine runs at proper idle speed.
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FUEL SYSTEM - Service Adjustment Procedures13-33THROTTLE BODY
(THROTrLE VALVE AREA)
CLEANINGM13FICS
(1) Start the engine, warm it up until engine coolant tempera-ture rises to
80°C (176”F), and stop the engine.
(2) Disconnect the air intake hose at the throttle body side.
(3) Put a plug in the inlet of bypass passage in the throttle
body.
CautionNever allow cleaning agent to flow into the bypass
passage.(4) Spray cleaning agent from the intake port of the throttle
body to the valve and leave as it is for 5 minutes or so.
(5) Start the engine and race it several times. Then, run it idlefor approx. one minute.
NOTE
If the engine idle speed becomes unstable (and fails in theworst case) after plugging the bypass passage, run the
engine with the throttle valve slightly opened.
(6) If the deposit cannot be removed from the throttle valve,
repeat steps (4) and (5).
(7) Disconnect the plug from the inlet of the bypass passage.(8) Install the air ‘intake hose.
(9) Use a multi-use tester to erase the self-diagnosis code ordisconnect the battery ground cable for more than
IOseconds and then connect it again.
(lO)Adjust the basic idle speed (speed adjusting screw). (Referto
P.13-31.)
7FUO629
ADJUSTMENT OF IDLE POSITION SWITCH AND
THROTTLE POSITION SENSOR (TPS)M13FIFA(1) Disconnect the throttle position sensor connector.
(2) Using jumper wires, connect an ohmmeter across terminal
@ (idle position switch) and terminal @ (sensor ground) ofthe throttle position sensor.
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FUEL SYSTEM - Service Adjustment Procedures
(3) Insert a 0.65-mm-thick feeler gauge between the fixed SASand throttle lever.
Terminal @
(sensor output)zensor g&nd)MB991348
1
(4) Loosen the throttle position sensor mounting bolts and turnthe TPS body fully counterclockwise.
(5) In this condition, check that there is continuity across
terminals
@ and @.
(6) Slowly turn the throttle position sensor clockwise until you
find a point at which there is no continuity across terminals
@ and 0. Then, tighten the throttle position sensor
mounting bolt securely.(7) Connect the throttle position sensor connector.
(8) When using the multi-use tester, connect it to the diagnosis
connector.
(9) When not using the multi-use tester, proceed as follows:
@ Disconnect the throttle position sensor connectors andconnect the special tool, Test Harness Set, between
the disconnected connectors.
@ Connect a digital voltmeter between the throttle posi-
tion sensor terminal @ (sensor output) and teminal @
(sensor ground).
(lO)Turn the ignition switch ON (but do not start the engine).
(IlKheck the throttle position sensor output voltage.
When using the multi-use tester, select item No. 14 and
read the throttle position sensor output voltage.
Standard value: 400 - 1,000 mV
(12)lf the voltage is out of specification, check the throttle
position sensor and associated harnesses.
(13)Remove the feeler gauge.
(14)Turn the ignition switch OFF.
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1

13-36FUEL SYSTEM - 0
n-vehicle Inspection of MPI Components
ON-VEHICLE INSPECTION OF MPI COMPONENTS
COMPONENTS LOCATION
EGR control solenoid valve
temperature sensor
Engine control unit
Engine coolant temperature sensor
Engine warning light
Fuel pressure control valve
Ignition coil (power transistor)
Ignition timing adjusting terminal
SSelf-diagnosis output terminal and self-diagnosis/Rdata transmission selector terminal
BTDC sensor and crank angle sensorD
PThrottle position sensor (with built-in idle switch)C
vVariable induction control servo (DC motor)J(with built-in induction control valve position
sensor)
MVehicle speed sensor (reed switch)F
QWaste gate solenoid valve U
NOTEThe “Name” column is in alphabetical order.TSB Revision

13-38FUEL SYSTEM - Onaehicle Inspection of MPI Components
I/ariableinduction control se:DC motor) (with built-in induction:ontrol valve position sensor)7FUO8
Engine warning
1 Self-diagn,osls output terminal
and self-dlagnosisi data
transmission selector terminal T37
h\s e >\\ 7FUO999Engiie
control
unit
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13-40FUEL SYSTEM -On-vehicle Inspection of MPI Components
COMPONENTS INSPECTION PROCEDUREM13YBAC
USING MULTI-USE TESTER
(1) Check by the service data and actuator test function. If any ij
abnormality is found, check the body harness, components,
etc. and repair as necessary.
(2) After repair, check again with the multi-use tester to makesure that the input and output signals are now normal.
(3) Erase the self-diagnosis trouble code in memory.
(4) Disconnect the multi-use tester.
(5) Start the engine and perform running test, etc. to make
sure that the troubles have been corrected.
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FUEL SYSTEM - On-vehicle Inspection of MPI Components13-41
POWER SUPPLY AND IGNITION SWITCH-IG
Engine control
unit
16FO29:
Q-i=++=
iA MPI control relay
ml3Yuu
lcmition switch (IG)
@ Harness sideccmnector
62
I
Engine control unit
Engine control unit connector7FUO950
OPERATIONl
While the ignition switch is on, battery power is supplied to the engine control unit, the injector, the airflow sensor, etc.
lWhen the ignition switch is turned on, the battery voltage is applied from the ignition switch to the engine
control unit, which then turns ON the power transistor to energize the control relay coil. This turns ON thecontrol relay switch and the power is supplied from the battery to the engine control unit through the
control relay switch.
INSPECTION
Using Multi-use Tester
IFunctionItem No.Data displayICheck conditionIStandard valueI
Data reading16Engine control unit
power voltageIgnition switch: ONsv
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