idle speed control MITSUBISHI MONTERO 1998 Service Manual










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g grams 

GND or GRND Ground 

GRN Green 

GRY Gray 

Ga. Gauge 

Gals. gallons 

Gov. Governor 











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"H" ABBREVIATION TABLE
"H" ABBREVIATION TABLE







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ABBREVIATION DEFINITION 










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H/D Heavy Duty 

HAC High Altitude Compensation 

HC Hydrocarbons 

HEDF High Speed Electro Drive Fan relay or circuit 

HEGO Heated Exhaust Gas Oxygen Sensor 

HEGOG HEGO Ground circuit 

HEI High Energy Ignition 

HLDT Headlight 

HO High Output 

HP High Performance 

HSC High Swirl Combustion 

HSO High Specific Output 

HTR Heater 

HVAC Heating 

Headlt. Headlight 

Hg Mercury 

Hgt. Height 

Htr. Heater 

Hz Hertz (Cycles Per Second) 











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"I" ABBREVIATION TABLE
"I" ABBREVIATION TABLE







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ABBREVIATION DEFINITION 










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I.D. Inside Diameter 

IAC Idle Air Control 

IACV Idle Air Control Valve 

IC Integrated Circuit 

ID Identification 

IDM Ignition Diagnostic Monitor 

IGN Ignition system or circuit 

ILC Idle Load Compensator 

In. Hg Inches of Mercury 

INCH Lbs. Inch Pounds 

INFL REST Inflatable Restraint 

INJ Injector or Injection 

IP Instrument Panel 

IPC Instrument Panel Cluster 

ISA Idle Speed Actuator 

ISC Idle Speed Control 

ISS Idle Stop Solenoid 

ITS Idle Tracking Switch 

IVSV Idle Vacuum Switching Valve 

distributor.
2) Start engine and warm engine until engine temperature
coolant is 176-203
F (80-95C). Turn engine off. Insert a paper clip
in engine speed detection connector terminal No. 3. See Fig. 1.
Connect a primary voltage detection-type tachometer to paper clip.
Fig. 1: Locating Engine Speed Detection Connector (Diamante)
Courtesy of Mitsubishi Motor Sales of America
3) Install a timing light. Start engine and allow it to idle.
Ensure engine curb idle speed is about 700 RPM. Curb idle speed is
automatically controlled by Idle Air Control (IAC) system. If curb
idle speed is not as specified, see DTC P0505 in G - TESTS W/CODES
article.
CAUTION: MFI system actuator test must be cancelled or test will
continue to run for 27 minutes. Driving vehicle under this
condition may damage engine.
4) Turn engine off. Connect scan tool to Data Link Connector
(DLC). DLC is located below left side of dash, near steering column.
See Fig. 2 . Start engine and allow it to idle. Using scan tool, select
MFI SYSTEM ACTUATOR TEST, then select item 17 (BASIC IGNITION TIMING).\
Press "Y" and read basic ignition timing value. See
IGNITION TIMING SPECIFICATIONS table. If basic ignition timing is
within specification, go to next step. If basic ignition timing is not
within specification, cancel MFI system actuator test. See DTC P0335
in G - TESTS W/CODES article.
5) Read actual ignition timing value. If actual ignition
timing is not within specification, cancel MFI system actuator test.
See DTC P0335 in G - TESTS W/CODES article.

coolant is 176-203F (80-95C). Turn engine off. Insert a paper clip
in engine speed detection connector. See Fig. 3. Connect a tachometer
to paper clip.
Fig. 3: Locating Engine Speed Detection Connector (3000GT - DOHC)
Courtesy of Mitsubishi Motor Sales of America
3) Install a timing light. Start engine and allow it to idle.
Using tachometer, read curb idle (RPM). Multiply RPM reading by 3 to
obtain actual curb idle speed. Ensure curb idle speed is 600-700 RPM.
Turn engine off. Curb idle speed is automatically controlled by Idle
Air Control (IAC) system. If curb idle speed is not as specified, see
DTC P0505 in G - TESTS W/CODES article.
4) Disconnect waterproof female connector from Brown ignition
timing check connector. See Fig. 4. Using a jumper wire, ground
ignition timing check terminal to read basic ignition timing. Using
timing light, read basic ignition timing value. See
IGNITION TIMING SPECIFICATIONS table. If basic ignition timing is
within specification, go to next step. If basic ignition timing is not
within specification, see DTC P0335 in G - TESTS W/CODES article.
5) Remove jumper wire to read actual ignition timing. Using
timing light, read actual ignition timing value. If actual ignition
timing is not within specification, see DTC P0335 in G - TESTS W/CODES
article.

Fig. 4: Locating Ignition Timing Check Connector
Courtesy of Mitsubishi Motor Sales of America
3000GT (SOHC)
1) Ignition timing is controlled by Powertrain Control Module
(PCM) and is not adjustable. Manufacturer provides procedure for
checking timing.
2) Start engine and warm engine until engine temperature
coolant is 176-203
F (80-95C). Turn engine off. Insert a paper clip
in noise filter connector. See Fig. 5. Connect a tachometer to paper
clip.
Fig. 5: Locating Noise Filter Connector
Courtesy of Mitsubishi Motor Sales of America
3) Install a timing light. Start engine and allow it to idle.
Using tachometer, read curb idle speed (RPM). Ensure curb idle speed

is 600-700 RPM. Turn engine off. Curb idle speed is automatically
controlled by Idle Air Control (IAC) system. If curb idle speed is not\
as specified, see DTC P0505 in G - TESTS W/CODES article.
4) Disconnect waterproof female connector from Brown ignition
timing check connector. See Fig. 4. Using a jumper wire, ground
ignition timing check terminal to read basic ignition timing. Using
timing light, read basic ignition timing value. See
IGNITION TIMING SPECIFICATIONS table. If basic ignition timing is
within specification, go to next step. If basic ignition timing is not
within specification, see DTC P0335 in G - TESTS W/CODES article.
5) Remove jumper wire to read actual ignition timing. Using
timing light, read actual ignition timing value. If actual ignition
timing is not within specification, see DTC P0335 in G - TESTS W/CODES
article.
All Other Models
1) Ignition timing is controlled by Powertrain Control Module
(PCM) and is not adjustable. Manufacturer provides procedure for
checking timing. On models with distributor, DO NOT attempt to adjust
ignition timing by rotating distributor.
2) Connect scan tool to Data Link Connector (DLC). DLC is
located below dash, near steering column. See Fig. 2. Install a timing
light. Start engine and allow it to idle.
3) Using scan tool, read curb idle speed (RPM). Ensure curb
idle speed is about 750 RPM. Turn engine off. Curb idle speed is
automatically controlled by Idle Air Control (IAC) system. If curb
idle speed is not as specified, see DTC P0505 in G - TESTS W/CODES
article.
CAUTION: MFI system actuator test must be cancelled or test will
continue to run for 27 minutes. Driving vehicle under this
condition may damage engine.
4) Using scan tool, select MFI SYSTEM ACTUATOR TEST, then
select item 17 (BASIC IGNITION TIMING). Read basic ignition timing
value. See IGNITION TIMING SPECIFICATIONS table. If basic ignition
timing is within specification, go to next step. If basic ignition
timing is not within specification, cancel MFI system actuator test.
See DTCS P0100 (except Mirage 1.5L), P0105, P0115 and P0335 in G -
TESTS W/CODES article.
5) Read actual ignition timing value. If actual ignition
timing is not within specification, cancel MFI system actuator test.
See DTCS P0100 (except Mirage 1.5L), P0105, P0115 and P0335 in G -
TESTS W/CODES article.
IDLE SPEED & MIXTURE
* PLEASE READ THIS FIRST *
NOTE: Perform adjustments with engine at normal operating
temperature, cooling fan and accessories off, transmission
in Park or Neutral, and front wheels in straight-ahead
position.
BASIC IDLE SPEED
NOTE: Basic idle speed adjustment information on Eclipse 2.0L
non-turbo engine is not available from manufacturer at time
of publication.
3000GT
1) Ensure vehicle is at normal operating temperature with all

Application Curb Idle Basic Idle
1.5L & 1.8L ............ 600-800 ............... 650-750
2.0L
Non-Turbo ............ 700-900 ................... (1)
Turbo ................ 650-850 ............... 700-800
2.4L ................... 650-850 ............... 700-800
3.0L & 3.5L ............ 600-800 ............... 650-750
( 1) - Information is not available from manufacturer at time
of publication.









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NOTE: Basic idle speed should only be adjusted after verifying
spark plugs, fuel injectors, idle air control motor and
engine compression are okay.
All Other Models
1) Ensure vehicle is at normal operating temperature with all
lights, cooling fan and accessories off. Shift transmission into
Neutral or Park position.
2) Basic idle speed can only be adjusted using a scan tool to
ground Data Link Connector (DLC). Connect scan tool to DLC. DLC is
located below dash, near steering column. See Fig. 2.
3) Start engine and allow it to idle. Using scan tool, select
MFI SYSTEM ACTUATOR TEST, then select item 30. Check basic idle speed.
See IDLE SPEED SPECIFICATIONS table.
CAUTION: MFI system actuator test must be cancelled or test will
continue to run for 27 minutes. Driving vehicle under this
condition may damage engine.
4) Cancel MFI system actuator test. If idle speed is not
within specification, turn engine speed adjusting screw until correct
engine speed is obtained. See Fig. 6. Access to speed adjusting screw
is obtained by removing rubber plug on throttle body.
5) If idle speed cannot be lowered by turning engine speed
adjusting screw, determine if fixed Speed Adjusting Screw (SAS). Fixed\
SAS is stop screw contacting throttle lever. See
FIXED SPEED ADJUSTING SCREW for procedure.
6) After all adjustments are verified to be correct, possible
cause of incorrect idle speed is deterioration of Idle Air Control
(IAC) circuit. See DTC P0505 in G - TESTS W/CODES article.
CURB (SLOW) IDLE SPEED
NOTE: Curb idle speed is controlled by Idle Air Control (IAC)
motor. Adjustment is usually not necessary. For curb idle
speed specifications, see IDLE SPEED SPECIFICATIONS table
under BASIC IDLE SPEED.
1) Check ignition timing and adjust if necessary. See
IGNITION TIMING . Run engine at 2000-3000 RPM for more than 5 seconds.
Allow engine to idle for 2 minutes. Check curb idle speed.
2) If curb idle speed is not within specification, check IAC
system. See DTC P0505 in G - TESTS W/CODES article. If IAC system is
okay, adjust basic idle speed. See BASIC IDLE SPEED.
FIXED SPEED ADJUSTING SCREW
NOTE: Fixed Speed Adjusting Screw (SAS) is preset by manufacturer
and usually does not require adjustment. Only adjust fixed
SAS if other adjustment procedures require it, or if

manufacturer's original setting has been changed.
1) Loosen throttle cable. Loosen fixed SAS lock nut. See
Fig. 7. Turn fixed SAS counterclockwise until throttle valve is fully
closed. Turn fixed SAS clockwise until throttle valve begins to open.
Turn fixed SAS clockwise 1 1/4 turns after throttle valve begins to
open.
2) Tighten lock nut while holding fixed SAS in position.
Adjust throttle cable. Adjust basic idle speed. See BASIC IDLE SPEED.
Adjust Throttle Position (TP) sensor. See TP SENSOR ADJUSTMENT under
THROTTLE POSITION (TP) SENSOR.
Fig. 7: Adjusting Fixed Speed Adjusting Screw (Typical)
Courtesy of Mitsubishi Motor Sales of America
IDLE MIXTURE
NOTE: Idle mixture is computer controlled on fuel injected engines
and is nonadjustable. CO level should not exceed .5%. HC
level should not exceed 100 ppm. If mixture levels exceed
limits, see G - TESTS W/CODES article.
THROTTLE POSITION (TP) SENSOR
TP SENSOR ADJUSTMENT
NOTE: Ensure basic idle speed is set to specification before
adjusting TP sensor. See BASIC IDLE SPEED under IDLE SPEED &

MIXTURE. Perform all adjustments with engine at normal
operating temperature, front wheels in straight-ahead
position, cooling fan and all accessories off, and
transmission in Park or Neutral.
Eclipse 2.0L Non-Turbo
1) TP sensor is not adjustable. Disconnect TP sensor
connector. Using external ohmmeter, measure resistance between TP
sensor terminals No. 1 and 3. See Fig. 8. If resistance is not 3500-
6500 ohms, replace TP sensor.
2) While slowly rotating throttle valve from idle to full
open, measure resistance between TP sensor terminals No. 2 and 3. If
resistance does not change smoothly in proportion to throttle opening,
replace TP sensor.
Montero
1) Disconnect TP sensor connector. Using jumper wires,
connect an external ohmmeter between TP sensor terminals No. 1 and 2.
See Fig. 9 . Insert .025" (.65 mm) feeler gauge between fixed speed
adjusting screw and throttle lever.
2) Loosen TP sensor mounting screws and rotate TP sensor
fully clockwise. Ensure there is continuity between terminals No. 1
and 2. Rotate TP sensor counterclockwise until there is no continuity,
and tighten screws. Install Test Harness (MB991348) between TP sensor
and harness connector.
3) Turn ignition on. Using external voltmeter, measure TP
sensor output voltage between terminals No. 1 and 3. If voltage is not
.4-1.0 volt, check harness and sensor. See DTC P0120 in G - TESTS
W/CODES article.
All Other Models
1) Disconnect TP sensor connector. Using jumper wires,
connect an external ohmmeter between TP sensor terminals No. 1 and 2
on Diamante or No. 3 and 4 on all other models. See Fig. 9. On
Diamante and Mirage 1.8L with cruise control, insert .055" (1.40mm)
feeler gauge between fixed speed adjusting screw and throttle lever.
On Galant, insert .025" (.65 mm) feeler gauge between fixed speed
adjusting screw and throttle lever. On all other models, insert .018"
(.45 mm) feeler gauge between fixed speed adjusting screw and throttle\
lever.
2) Loosen TP sensor mounting screws and rotate TP sensor
fully counterclockwise. Ensure there is continuity between terminals
No. 1 and 2 on Diamante, or No. 3 and 4 on all other models. Rotate TP
sensor clockwise until there is no continuity and tighten screws.
Install Test Harness (MB991348) between TP sensor and harness
connector.
3) Turn ignition on. Using external voltmeter, measure TP
sensor output voltage between terminals No. 1 and 3 on Diamante, or
No. 2 and 4 on all other models. If voltage is not .4-1.0 volt, check
harness and sensor. See DTC P0120 in G - TESTS W/CODES article.
Fig. 8: TP Sensor Connector Terminals (Eclipse 2.0L Non-Turbo)
Courtesy of Mitsubishi Motor Sales of America

E - THEORY/OPERATION
1998 Mitsubishi Montero
1998 ENGINE PERFORMANCE
Mitsubishi - Theory & Operation
Diamante, Eclipse, Galant, Mirage, Montero, Montero Sport,
3000GT
INTRODUCTION
This article covers basic description and operation of engine
performance-related systems and components. Read this article before
diagnosing vehicles or systems with which you are not completely
familiar.
AIR INDUCTION SYSTEM
NON-TURBOCHARGED ENGINES
Mirage equipped with 1.5L engine uses a Manifold Absolute
Pressure (MAP) sensor instead of a Volume Airflow (VAF) sensor.
Filtered air is ducted to a plenum-mounted throttle body.
All other models use same basic air induction system using a
remote air filter (with VAF sensor) connected to a plenum-mounted
throttle body.
TURBOCHARGED ENGINES
In addition to basic air induction system, turbocharging
system components include turbocharger(s), charge air cooler(s), air\
by-pass valve(s), wastegate actuator(s), wastegate control solenoid
valve(s) and intake duct(s).
Wastegate Control Solenoid Valve(s)
Powertrain Control Module (PCM) energizes solenoid valve(s)\
,
controlling bleed-off rate of turbocharger pressure by wastegate
actuator(s).
COMPUTERIZED ENGINE CONTROLS
Sequential Fuel Injection (SFI) is a computerized engine
control system, which controls fuel injection, ignition timing, idle
speed and emission control systems.
POWERTRAIN CONTROL MODULE (PCM)
PCM, also known as Engine Control Module (ECM), receives and
processes signals from input devices. Operating conditions such as
cold starting, altitude, acceleration and deceleration affect input
device signals. Based on signals received, PCM sends signals to
various components, which control fuel injection, ignition timing,
idle speed and emission control systems. For PCM location, see
PCM LOCATION table.
PCM LOCATION TABLE









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Application Location
Eclipse 2.0L Non-Turbo .......... In Front of Left Front Strut Tower

Mirage &
Montero Sport ... Behind Right Side Of Instrument Panel (Glove Box)\
Montero ..................................... Right Front Kick Panel
All Others ................................... Behind Center Console









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NOTE: Components are grouped into 2 categories. The first category
covers INPUT DEVICES, which control or produce voltage
signals monitored by Powertrain Control Module (PCM). The
second category covers OUTPUT SIGNALS, which are components
controlled by PCM.
INPUT DEVICES
Vehicles are equipped with different combinations of input
devices. Not all input devices are used on all models. To determine
input device usage on specific models, see appropriate wiring diagram
in L - WIRING DIAGRAMS article. The following are available input
devices.
Air Conditioning Switch
When A/C is turned on, signal is sent to PCM. With engine at
idle, PCM increases idle speed through Idle Air Control (IAC) motor.
Airflow Sensor Assembly
Assembly is mounted inside air cleaner, and incorporates
barometric pressure sensor, intake air temperature sensor and volume
airflow sensor.
Barometric (BARO) Pressure Sensor
Sensor is incorporated into airflow sensor assembly. Sensor
converts barometric pressure to electrical signal, which is sent to
PCM. PCM adjusts air/fuel ratio and ignition timing according to
altitude.
Camshaft Position (CMP) Sensor
On SOHC engines equipped with a distributor, CMP sensor is
located in distributor. On Eclipse (Turbo) and DOHC V6 engines, sensor\
is located beside camshaft, in front of engine. On all other engines,
CMP sensor is a separate unit mounted in place of distributor. PCM
determines TDC based on pulse signals received from sensor, and then
controls MFI timing.
Closed Throttle Position (CTP) Switch
CTP switch is located in the Throttle Position (TP) sensor.
PCM senses whether accelerator pedal is depressed or not. High voltage
(open) or low voltage (closed) signal is input to PCM, which then
controls Idle Air Control (IAC) motor based on input signal.
Crankshaft Position (CKP) Sensor
CKP sensor is located in distributor on SOHC engines, except
1.5L 4-cylinder with California emissions. On DOHC 4-cylinder, DOHC V6
and 1.5L 4-cylinder engines with California emissions, CKP sensor is
located beside crankshaft, in front of engine. PCM determines
crankshaft position on pulse signals received from sensor, and then
controls MFI timing and ignition timing.
Engine Coolant Temperature (ECT) Sensor
ECT sensor converts coolant temperature to electrical signal
for use by PCM. PCM uses coolant temperature information to control
fuel enrichment when engine is cold.
Heated Oxygen Sensor (HO2S)