Mitsubishi Montero (1991+). Manual - part 287

         See FUEL DELIVERY under FUEL SYSTEM.

         Idle Speed Control Servo

         See IDLE SPEED under FUEL SYSTEM.

         Power Transistor(s) & Ignition Coils

         See IGNITION SYSTEMS.

         Purge Control Solenoid Valve

         See EVAPORATIVE CONTROL under EMISSION SYSTEMS.

         Self-Diagnostic Connector

         See SELF-DIAGNOSTIC SYSTEM.

         Wastegate Control Solenoid Valve

         See TURBOCHARGED ENGINES under AIR INDUCTION SYSTEM.

         FUEL SYSTEM

         FUEL DELIVERY

         Electric fuel pump (located in gas tank) feeds fuel through

in-tank fuel filter, external fuel filter (located in engine

compartment) and fuel injector rail.

         Fuel Pump

         Consists of an impeller driven by a motor. Pump has an

internal check valve to maintain system pressure and a relief valve to

protect the fuel pressure circuit. Pump receives voltage supply from

Multi-Point Injection (MPI) control relay.

         Fuel Pressure Control Solenoid Valve (Turbo Only)

         Prevents rough idle due to fuel percolation. On engine

restart, if engine coolant or intake air temperatures reach a preset

value, ECU applies voltage to fuel pressure control solenoid valve for

2 minutes after engine re-start. Valve opens, allowing atmospheric

pressure to be applied to fuel pressure regulator diaphragm. This

allows maximum available fuel pressure at injectors, enriching fuel

mixture and maintaining stable idle at high engine temperatures.

         Fuel Pressure Regulator

         Located on fuel injector rail, this diaphragm-operated relief

valve adjusts fuel pressure according to engine manifold vacuum.

         As engine manifold vacuum increases (closed throttle), fuel

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). ECU controls amount

of fuel metered through injectors based upon information received from

sensors.

         IDLE SPEED

         Air Conditioner Relay

         When A/C is turned on with engine at idle, ECU signals ISC

motor to increase idle speed. To prevent A/C compressor from switching

on before idle speed has increased, ECU momentarily opens A/C relay

circuit.

         Idle Speed Control (ISC) Motor

         Controls pintle-type air valve (DOHC engines) or throttle

plate angle (SOHC engines) to regulate volume of intake air at idle.

         During start mode, ECU controls idle intake air volume

according to coolant temperature input. After starting, with idle

position switch activated (throttle closed), fast idle speed is

controlled by ISC motor and fast idle air control valve (if equipped).

         When idle switch is deactivated (throttle open), ISC motor

moves to a preset position in accordance with coolant temperature

input.

         When automatic transmission (if equipped) is shifted from

Neutral to Drive, A/C is turned on or power steering pressure reaches

a preset value, ECU signals ISC motor to increase engine RPM.

         Fast Idle Air Control Valve

         Some models use a coolant temperature-sensitive fast idle air

control valve, located on throttle body, to admit additional intake

air volume during engine warm-up. Control valve closes as temperature

increases, restricting by-pass airflow rate. At engine warm-up, valve

closes completely.

         IGNITION SYSTEMS

         DIRECT IGNITION SYSTEM (DIS) - DOHC ENGINES

         Ignition system is a 2-coil, distributorless ignition system.

Crankshaft angle and TDC sensor assembly, mounted in place of

distributor, are optically controlled.

         Power Transistors & Ignition Coils

         Based on crankshaft angle and TDC sensor inputs, ECU controls

timing and directly activates each power transistor to fire coils.

Power transistor "A" controls primary current of ignition coil "A" to

fire spark plugs on cylinders No. 1 and 4 at the same time. Power

transistor "B" controls primary current of ignition coil "B" to fire

spark plugs on cylinders No. 2 and 3 at the same time.

         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.

         ELECTRONIC IGNITION SYSTEM - SOHC ENGINES

         Mitsubishi breakerless electronic ignition system uses a disc

and optical sensing unit to trigger power transistor.

         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. ECU 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 ECU. ECU adjusts timing

based upon various conditions, such as engine temperature, altitude

and detonation (turbo vehicles only).

         EMISSION SYSTEMS

         EXHAUST GAS RECIRCULATION (EGR) CONTROL

         Federal (Non-Turbocharged)

         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 thermovalve 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 and

allows exhaust gases to flow into intake manifold for combustion.

         California & Turbocharged

         ECU controls EGR operation by activating EGR control solenoid

valve according to engine load. When engine is cold, ECU signals EGR

control solenoid valve to deactivate EGR.

         California models are equipped with an EGR temperature

sensor. When EGR malfunction occurs, EGR temperature decreases and ECU

illuminates CHECK ENGINE (malfunction indicator) light.

         EGR Control Solenoid Valve

         Denies or allows vacuum supply to EGR valve, based upon ECU

commands.

         Thermovalve

         Denies or allows vacuum supply to EGR valve based on coolant

temperature.

         EVAPORATIVE CONTROL

         Fuel evaporation system prevents fuel vapor from entering

atmosphere. System consists of a special fuel tank with vapor

separator tanks (if equipped), vacuum relief filler cap, overfill

limiter (2-way 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

         When engine is off, fuel vapors are vented into charcoal

canister. When engine is warmed to normal operating temperature and

running above idle, ECU energizes purge control solenoid valve,

allowing vacuum to purge valve.

         Canister vapors are then drawn through purge valve into

intake manifold for burning. Purge control solenoid valve remains

closed during idle and engine warm-up to reduce HC and CO emissions.

         HIGH ALTITUDE CONTROL (HAC)

         This system compensates for variations in altitude. When

atmospheric (barometric) pressure sensor determines vehicle is above

preset altitude, ECU compensates by adjusting air/fuel mixture and

ignition timing. If HAC system is inoperative, there will be an

increase in emissions.

         PCV VALVE

         Positive Crankcase Ventilation (PCV) valve operates in the

closed crankcase ventilation system. Closed crankcase ventilation

system consists of PCV valve, oil separator, breather and ventilation

hoses.

         PCV valve is a one-way check valve, located in valve cover.

When engine is running, manifold vacuum pulls PCV valve open, allowing

crankcase fumes to enter intake manifold. If engine backfires through

intake manifold, PCV valve closes to prevent crankcase combustion.

         SELF-DIAGNOSTIC SYSTEM

         Self-diagnostic system monitors input and output signals. On

all models, codes can be read using analog voltmeter. On some models,

scan tool can be used to read codes. For additional information, see G

- TESTS W/ CODES article.

         CHECK ENGINE Light

         Also called Malfunction Indicator Light by manufacturer,

comes on when ignition is turned on. Light remains on for several

seconds after engine has started. If an abnormal input signal occurs,

light comes on and code is stored in memory. If an abnormal input

signal returns to normal, ECU turns light off but code remains stored

in memory until cleared. If ignition is turned on again, light will

not come on until ECU detects malfunction during system operation.

NOTE:    ECU diagnostic memory is retained by direct power supply

         from the battery. Memory is not erased by turning off

         ignition but is erased if battery or ECU is disconnected.