1998 MITSUBISHI MONTERO timing

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)

HO2S detects oxygen content in exhaust gas and sends this
information to PCM. PCM uses input signals from HO2S to vary duration
of fuel injection. HO2S heater stabilizes sensor temperature
regardless of exhaust gas temperature to allow for more accurate
exhaust oxygen content readings.
Idle Air Control (IAC) Valve Position Sensor
Sensor is incorporated in IAC motor. Sensor senses IAC motor
plunger position and sends electrical signal to PCM.
Ignition Timing Adjustment Terminal
Used for adjusting base ignition timing. When terminal is
grounded, PCM timing control function is by-passed, allowing base
timing to be adjusted.
Intake Air Temperature (IAT) Sensor
IAT sensor is incorporated into airflow sensor assembly. This
resistor-based sensor measures temperature of incoming air and
supplies air density information to PCM.
Knock Sensor (KS)
KS is located in cylinder block and senses engine vibration
during detonation (knock). KS converts vibration into electrical
signal. PCM retards ignition timing based on this signal.
Manifold Differential Pressure (MDP) Sensor
MDP sensor converts negative air pressure in intake manifold
plenum into voltage signals sent to PCM. PCM monitors Exhaust Gas
Recirculation (EGR) system using these signals.
Park/Neutral Position (PNP) Switch (Automatic Transmission)
PNP switch senses position of transmission select lever,
indicating engine load due to automatic transmission engagement. Based
on this signal, PCM commands IAC motor to increase throttle angle,
maintaining optimum idle speed.
Power Steering Oil Pressure Switch
Switch detects increase in power steering oil pressure. When
power steering oil pressure increases, switch contacts close,
signaling PCM. PCM commands IAC motor, raising idle speed to
compensate for drop in engine RPM due to power steering load.
Throttle Position (TP) Sensor
TP sensor is a variable resistor mounted on throttle body.
PCM uses voltage signal from TP sensor to determine throttle plate
angle.
Vehicle Speed Sensor (VSS)
Mounted on transaxle/transmission, VSS sends a pulsing signal
to PCM for vehicle speed calculation. PCM uses this calculation for
cruise control and fuel cut-off.
Volume Airflow (VAF) Sensor
Incorporated into airflow sensor assembly, VAF sensor
measures intake airflow rate. Intake air flows through tunnel in
airflow sensor assembly. VAF sensor sends frequency signal to PCM. PCM
uses signal to adjust fuel injection rate.
OUTPUT SIGNALS
NOTE: Vehicles are equipped with various combinations of
computer-controlled components. Not all components listed
below are used on every vehicle. To determine component

pressure regulator diaphragm opens relief valve, allowing pressure to
bleed off through fuel return line, reducing fuel pressure.
As engine manifold vacuum decreases (open throttle), fuel
pressure regulator diaphragm closes valve, preventing pressure from
bleeding off through fuel return line, increasing fuel pressure.
FUEL CONTROL
Fuel Injectors
Fuel is supplied to engine through electronically pulsed
(timed) injector valves located on fuel rail(s). PCM controls amount\
of fuel metered through injectors based on information received from
sensors.
IDLE SPEED
Air Conditioning (A/C) Relay
When A/C is turned on with engine at idle, PCM signals IAC
motor to increase idle speed. To prevent A/C compressor from switching
on before idle speed has increased, PCM momentarily opens A/C relay
circuit.
Idle Air Control (IAC) Motor
Motor controls pintle-type air valve to regulate volume of
intake air at idle.
During start mode, PCM controls idle intake air volume
according to Engine Coolant Temperature (ECT) sensor input. After
starting, with idle position switch activated (throttle closed), fast
idle speed is controlled by IAC motor and fast idle air control valve
(if equipped).
When idle switch is deactivated (throttle open), IAC motor
moves to a preset position in accordance with ECT sensor input.
PCM signals IAC motor to increase engine RPM in the following
situations: A/T (if applicable) is shifted from Neutral to Drive, A/C
is turned on, or power steering pressure reaches a preset value.
IGNITION SYSTEMS
DIRECT IGNITION SYSTEM (DIS)
Depending on number of cylinders, ignition system is a 2 or
3-coil, distributorless ignition system. On Eclipse (Turbo) and DOHC
V6 engines, Camshaft Position (CMP) sensor is located beside camshaft,\
in front of engine. On all other engines equipped with DIS, CMP sensor
is a separate unit mounted in place of distributor. On DOHC 4-
cylinder, DOHC V6 and 1.8L 4-cylinder engines with California
emissions, Crankshaft Position (CKP) sensor is located beside
crankshaft, in front of engine. PCM determines TDC based on pulse
signals received from sensors and then controls MFI and ignition
timing.
Power Transistors & Ignition Coils
Based on crankshaft position and CMP sensor inputs, PCM
controls timing and directly activates each power transistor to fire
coils. On 4-cylinder engines, power transistor "A" controls primary
current of ignition coil "A" to fire spark plugs on cylinders No. 1
and No. 4 at the same time. Power transistor "B" controls primary
current of ignition coil "B" to fire spark plugs on cylinders No. 2
and No. 3 at the same time. On V6 engines, companion cylinders No. 1
and 4, 2 and 5, and 3 and 6 are fired together.
On all models, although each coil fires 2 plugs at the same
time, ignition takes place in only one cylinder, since the other

cylinder is on its exhaust stroke when plug fires.
HALL EFFECT IGNITION SYSTEM
This system is equipped with a Hall Effect distributor.
Shutter(s) attached to distributor shaft rotate through distributor
Hall Effect switch, also referred to as a Camshaft Position (CMP)
sensor, which contains a distributor pick-up (a Hall Effect device and
magnet). As shutter blade(s) pass through pick-up, magnetic field is
interrupted and voltage is toggled between high and low. PCM uses this
data along with Crankshaft Position (CKP) sensor data to control
ignition timing and injector pulse width to maintain optimum
driveability.
Power Transistor & Ignition Coil
Power transistor is mounted inside distributor with disc and
optical sensing unit. When ignition is on, ignition coil primary
circuit is energized. As distributor shaft rotates, disc rotates,
triggering optical sensing unit. PCM receives signals from optical
sensing unit. Signals are converted and sent to power transistor,
interrupting primary current flow and inducing secondary voltage.
IGNITION TIMING CONTROL SYSTEM
Ignition timing is controlled by PCM. PCM adjusts timing
based on various conditions such as engine temperature, altitude and
detonation.
EMISSION SYSTEMS
EXHAUST GAS RECIRCULATION (EGR) CONTROL
Federal Emissions (Non-Turbo)
To lower oxides of nitrogen (NOx) exhaust emissions, a non-
computer controlled exhaust gas recirculation system is used. EGR
operation is controlled by throttle body ported vacuum. Vacuum is
routed through vacuum control valve to prevent EGR operation at low
engine temperatures.
Spring pressure holds EGR valve closed during low vacuum
conditions (engine idling or wide open throttle). When vacuum pressure\
increases and overcomes EGR spring pressure, EGR valve is lifted to
allow exhaust gases to flow into intake manifold for combustion.
California Emissions & Turbo
PCM controls EGR operation by activating EGR control solenoid
valve according to engine load. When engine is cold, PCM signals EGR
control solenoid valve to deactivate EGR.
EGR Control Solenoid Valve
Valve denies or allows vacuum supply to EGR valve based on
PCM commands.
EVAPORATIVE CONTROL
Fuel evaporation system prevents fuel vapor from entering
atmosphere. System consists of special fuel tank with vapor separator
tanks (if equipped), vacuum relief filler cap, overfill limiter (2-wa\
y
valve), fuel check valve, thermovalve (if equipped), charcoal
canister, purge control valve, purge control solenoid valve, and
connecting lines and hoses.
Purge Control Solenoid Valve

Fuel Pump Check Connector Taped to wiring harness, on
right side of firewall.
Ignition Timing Adjustment
Connector Taped to wiring harness, on
right side of firewall.
Ignition Coil Top left side of engine.

NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
CLEANING & INSPECTION
Clean camshaft with solvent. Ensure all oil passages are
clear. Inspect cam lobes and bearing journals for pitting, flaking or
scoring. Using micrometer, measure bearing journal O.D.
Support camshaft at each end with "V" blocks. Position dial
indicator with tip resting on center bearing journal. Rotate camshaft
and note reading. If reading exceeds specification, replace camshaft.
Check cam lobe lift by measuring base circle of camshaft
using micrometer. Measure again at 90 degrees to tip of cam lobe. Cam
lift can be determined by subtracting base circle diameter from tip of
cam lobe measurement.
Different lift dimensions are given for intake and exhaust
cam lobes. Reading must be within specifications. Replace camshaft if
cam lobes or bearing journals are not within specifications.
Inspect camshaft gear for chipped, eroded or damaged teeth.
Replace gear if damaged. On camshafts using thrust plate, measure
distance between thrust plate and camshaft shoulder. Replace thrust
plate if not within specification.
CAMSHAFT BEARINGS
Removal & Installation
Remove the camshaft rear plug. The camshaft bearing remover
is assembled with its shoulder resting on the bearing to be removed
according to manufacturer's instructions. Tighten puller nut until
bearing is removed. Remove remaining bearings, leaving front and rear
bearings until last. These bearings act as guide for camshaft bearing
remover.
To install new bearings, puller is rearranged to pull
bearings toward the center of block. Ensure all lubrication passages
of bearing are aligned with cylinder block. Coat new camshaft rear
plug with sealant. Install camshaft rear plug. Ensure plug is even
in cylinder block.
CAMSHAFT INSTALLATION
Lubricate bearing surfaces and cam lobes with ample amount of
Molykote or camshaft lubricant. Carefully install camshaft. Use care
not to damage bearing journals during installation. Install thrust
plate retaining bolts (if equipped). Tighten bolts to specification.
On overhead camshafts, install bearing caps in original location.
Tighten bolts to specification. Check end play.
CAMSHAFT END PLAY
Using dial indicator, check end play. Position dial indicator
on front of engine block. Position indicator tip against camshaft.
Push camshaft toward rear of engine and adjust indicator to zero.
Move camshaft forward and note reading. Camshaft end play
must be within specification. End play may be adjusted by relocating
gear, shimming thrust plate or replacing thrust plate depending on
manufacturer.
TIMING CHAINS & BELTS

* PLEASE READ THIS FIRST *
NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
TIMING CHAINS
Timing chains will stretch during operation. Limits are
placed upon amount of stretch before replacement is required. Timing
chain stretch will alter ignition timing and valve timing.
To check timing chain stretch, rotate crankshaft to eliminate
slack from one side of timing chain. Mark reference point on cylinder
block. Rotate crankshaft in opposite direction to eliminate slack from
remaining side of timing chain. Force other side of chain outward
and measure distance between reference point and timing chain. See
Fig. 23 . Replace timing chain and gears if not within specification.
Fig. 23: Measuring Timing Chain Stretch - Typical
This Graphic For General Information Only
Timing chains must be installed so that timing marks on
camshaft gear and crankshaft gear are aligned according to