1991 MITSUBISHI MONTERO air condition

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

Defective diodes or stator See Bench Test in
ALTERNATOR article









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Battery Does Loose or worn drive belt Check alternator drive
Stay Charged belt tension and
condition. See
Belt Adjustment in
appropriate TUNE-UP
article in the
TUNE-UP section
Loose or corroded battery Check all charging
connections system connections
Loose alternator connections Check all charging
system connections
Defective alternator or See On-Vehicle Tests
battery and Bench Tests in
ALTERNATOR article
Add-on electrical accessories Install larger
exceeding alternator capacity alternator









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Battery Defective battery Check alternator
Overcharged- output and repair as
Uses Too Much necessary
Water
Defective alternator See On-Vehicle Test and
Bench Tests in
ALTERNATOR article
Excessive alternator voltage Check alternator output
and repair as necessary









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IGNITION SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
Ignition Secondary Trouble Shooting Chart








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START: Visually inspect Spark Plug Wires, Coil Wires, 

Plug Wire Boots, Rotor, and Distributor Cap for 

signs of damage. 










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OK   NOT OK 




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* To test secondary ignition   * Repair or replace 

system, modify a Spark Plug   damaged components 

by attaching a ground wire   as necessary 

to the body of the plug and  









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 OK   NOT OK  




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* Check Pick-Up coil for   * Adjust or replace as  

correct resistance value.   necessary.  










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NOT OK   OK  








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* Replace Pick-Up coil if   * Check control module for  

not to specification.   good ground connections.  










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OK  




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* If vehicle fails to run at this point, go to  
 the appropriate article in the ENGINE  
 PERFORMANCE section.  









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OK   NOT OK 




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* Check wires from the battery/  * Replace ballast resistor 

ignition switch to the coil.   if the measured resistance 

Also check the coil primary   value is not within 

and secondary resistance.   specification. 










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STARTER TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC STARTER TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Starter Fails Dead battery or bad Check battery charge
to Operate connections between and all wires and
starter and battery connections to starter
Ignition switch faulty Adjust or replace
or misadjusted ignition switch
Open circuit between Check and repair wires
starter switch ignition and connections as
terminal on starter relay necessary
Starter relay or starter See Testing in STARTER
defective article

Fires With Key Flywheel runout contributes
released. Engine to the intermittent nature
Fires and Cranks
Normally









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AIR CONDITIONING & HEAT
AIR CONDITIONING TROUBLE SHOOTING
WARNING: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC AIR CONDITIONING TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE








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Compressor Not Working
Compressor clutch circuit open.

Compressor clutch coil inoperative.

Poor clutch ground connection.

Fan belts loose.

Thermostatic switch inoperative.

Thermostatic switch not adjusted.

Ambient temperature switch open.

Superheat fuse blown.








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Excessive Noise or Vibration
Missing or loose mounting bolts.

Bad idler pulley bearings.

Fan belts not tightened correctly.

Compressor clutch contacting body.

Excessive system pressure.

Compressor oil level low.

Damaged clutch bearings.

Damaged reed valves.

Damaged compressor.








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Insufficient or No Cooling;
Compressor Working
Expansion valve inoperative.

Heater control valve stuck open.

Low system pressure.

Blocked condenser fins.

Blocked evaporator fins.

Vacuum system leak.

Vacuum motors inoperative.

Control cables improperly adjusted.

Restricted air inlet.

Mode doors binding.

Blower motor inoperative.

Temperature above system capacity.








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HEATER SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to

problem symptoms. For model-specific Trouble Shooting,
refer to DIAGNOSTIC, or TESTING articles available in the
section(s) you are accessing.
BASIC HEATER SYSTEM TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE








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Insufficient, Erratic,
or No Heat
Low Coolant Level

Incorrect thermostat.

Restricted coolant flow through
heater core.


Heater hoses plugged.

Misadjusted control cable.

Sticking heater control valve.

Vacuum hose leaking.

Vacuum hose blocked.

Vacuum motors inoperative.

Blocked air inlet.

Inoperative heater blower motor.

Oil residue on heater core fins.

Dirt on heater core fins.








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Too Much Heat
Improperly adjusted cables.

Sticking heater control valve.

No vacuum to heater control valve.

Temperature door stuck open.








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Air Flow Changes During
Acceleration
Vacuum system leak.

Bad check valve or reservoir.








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Air From Defroster At All
Times
Vacuum system leak.

Improperly adjusted control cables.

Inoperative vacuum motor.








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Blower Does Not Operate
Correctly
Blown fuse.

Blower motor windings open.

Resistors burned out.

Motor ground connection loose.

Wiring harness connections loose.

Blower motor switch inoperative.

Blower relay inoperative.

Fan binding or foreign object
in housing.


Fan blades broken or bent.








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BRAKES
BRAKE SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.

in the section(s) you are accessing.
BASIC GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Lopes At Intake manifold-to-head Replace manifold
Idle leaks gasket, See ENGINES
Blown head gasket Replace head gasket,
See ENGINES
Worn timing gears, chain Replace gears, chain or
or sprocket sprocket
Worn camshaft lobes Replace camshaft, See
ENGINES
Overheated engine Check cooling system,
See COOLING
Blocked crankcase vent Remove restriction
valve
Leaking EGR valve Repair leak and/or
replace valve
Faulty fuel pump Replace fuel pump









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Engine Has Low Leaking fuel pump Repair leak and/or
Power replace fuel pump
Excessive piston-to-bore Install larger pistons,
clearance See ENGINES
Sticking valves or weak Check valve train
valve springs components, See ENGINES
Incorrect valve timing Reset valve timing, See
ENGINES
Worn camshaft lobes Replace camshaft, See
ENGINES
Blown head gasket Replace head gasket.
See ENGINES.
Clutch slipping Adjust pedal and/or
replace components, See
ENGINES
Engine overheating Check cooling system,
See COOLING
Auto. Trans. pressure
regulator valve faulty Replace pressure
regulator valve
Auto. Trans. fluid level Add fluid as necessary
too low
Improper vacuum diverter
valve operation Replace vacuum diverter
valve
Vacuum leaks Inspect vacuum system
and repair as required
Leaking piston rings Replace piston rings,
See ENGINES









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Faulty High Low fuel pump volume Replace fuel pump
Speed Operation
Leaking valves or worn Replace valves and/or
springs, See ENGINES
Incorrect valve timing Reset valve timing,See
ENGINES
Intake manifold restricted Remove restriction
Worn distributor shaft Replace distributor









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Faulty Improper fuel pump stroke Remove pump and reset
Acceleration pump stroke

cracked or broken manifold, See ENGINES








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ENGINE PERFORMANCE
CARBURETOR TROUBLE SHOOTING:
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC COLD START SYMPTOMS TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Won't Choke not closing Check choke
Start operation, see
FUEL SYSTEMS
Choke linkage bent Check linkage, see
FUEL SYSTEM









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Engine Starts, Choke vacuum kick setting Check setting and
Then Dies too wide adjust see, FUEL
SYSTEMS
Fast idle RPM too low Reset RPM to specif-
ication, see TUNE-UP
Fast idle cam index Reset fast idle cam
incorrect index, see FUEL
SYSTEMS
Vacuum leak Inspect vacuum
system for leaks
Low fuel pump outlet Repair or replace
pump, see FUEL
SYSTEMS
Low carburetor fuel level Check float setting
see FUEL SYSTEM









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Engine Quits Choke vacuum kick setting Reset vacuum kick
Under Load incorrect setting,see FUEL
SYSTEMS
Fast idle cam index Reset fast idle cam
incorrect index, see FUEL
SYSTEM
Incorrect hot fast idle Reset fast idle RPM,
speed RPM see TUNE-UP









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Engine Starts, Choke vacuum kick set too Reset vacuum kick,
Runs Up,Then narrow see FUEL SYSTEMS
Idles, Slowly
With Black Smoke Fast idle cam index Reset fast idle cam

incorrect index, see FUEL
SYSTEMS
Hot fast idle RPM too low Reset fast idle RPM,
see TUNE-UP









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BASIC HOT START SYMPTOMS TROUBLE SHOOTING CHART








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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Won't Engine flooded Allow fuel to
Start evaporate









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BASIC COLD ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING CHART








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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Stalls in Choke vacuum kick setting Reset choke vacuum
Gear incorrect kick, see FUEL
SYSTEMS
Fast idle RPM incorrect Reset fast idle RPM,
see TUNE-UP
Fast idle cam index Reset fast idle cam
incorrect see FUEL SYSTEMS









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Acceleration Sag Defective choke control Replace choke
or Stall switch control switch
Choke vacuum kick setting Reset choke vacuum
incorrect kick see, FUEL
SYSTEMS
Float level incorrect Adjust float level,
(too low) FUEL SYSTEMS
Accelerator pump defective Repair or replace
pump see FUEL
SYSTEMS
Secondary throttles not Inspect lockout
closed adjustment,see FUEL
SYSTEMS









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Sag or Stall Defective choke control Replace choke
After Warmup switch control switch, see
FUEL SYSTEMS
Defective accelerator pump Replace pump, see
FUEL SYSTEMS
Float level incorrect Adjust float level,
(too low) see FUEL SYSTEMS









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Backfiring & Plugged heat crossover Remove restriction
Black Smoke system









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BASIC WARM ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING CHART








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