Mitsubishi Montero (1998+). Manual - part 137

Fig. 14:  Typical Pulsed Secondary Air Injection System

Courtesy of General Motors Corp.

         OXYGEN SENSOR (O2)

         The O2 sensor is mounted in the exhaust system where it

monitors oxygen content of exhaust gases. Some vehicles may use 2 O2

sensors. The O2 sensor produces a voltage signal which is proportional

to exhaust gas oxygen concentration (0-3%) compared to outside oxygen

(20-21%). This voltage signal is low (about .1 volt) when a lean

mixture is present and high (1.0 volt) when a rich mixture is present.

         As ECM compensates for a lean or rich condition, this voltage

signal constantly fluctuates between high and low, crossing a

reference voltage supplied by the ECM on the O2 signal line. This is

referred to as cross counts. A problem in the O2 sensor circuit should

set a related trouble code.

         COMPUTERIZED ENGINE CONTROLS (CEC)

         The CEC system monitors and controls a variety of

engine/vehicle functions. The CEC system is primarily an emission

control system designed to maintain a 14.7:1 air/fuel ratio under most

operating conditions. When the ideal air/fuel ratio is maintained, the

catalytic converter can control oxides of nitrogen (NOx), hydrocarbon

(HC) and carbon monoxide (CO) emissions.

         The CEC system consists of the following sub-systems:

Electronic Control Module (ECM), input devices (sensors and switches)

and output signals.

         EARLY FUEL EVAPORATION (EFE)

         The EFE valve is actuated by either a vacuum actuator or a

bimetal spring (heat-riser type). The EFE valve is closed when engine

is cold. The closed valve restricts exhaust gas flow from the exhaust

manifold. This forces part of the exhaust gas to flow up through a

passage below the carburetor. As the exhaust gas quickly warms the

intake mixture, distribution is improved. This results in better cold

engine driveability, shorter choke periods and lower emissions.

         Ensure EFE valve in exhaust manifold is not frozen or rusted

in a fixed position. On vacuum-actuated EFE system, check EFE thermal

vacuum valve and check valve(s). Also check for proper vacuum hose

routing. See Fig. 15.

Fig. 15:  Typical Vacuum-Actuated EFE System

Courtesy of General Motors Corp.

         EMISSION MAINTENANCE REMINDER LIGHT (EMR) (IF EQUIPPED)

         If equipped, the EMR light (some models may use a reminder

flag) reminds vehicle operator that an emission system maintenance is

required. This indicator is activated after a predetermined

time/mileage.

         When performing a smog check inspection, ensure EMR indicator

is not activated. On models using an EMR light, light should glow when

ignition switch is turned to ON position and should turn off when

engine is running.

         If an EMR flag is present or an EMR light stays on with

engine running, fail vehicle and service or replace applicable

emission-related components. To reset an EMR indicator, refer to

appropriate MAINTENANCE REMINDER LIGHTS in the MAINTENANCE section.

         MALFUNCTION INDICATOR LIGHT (MIL)

         The Malfunction Indicator Light (MIL) is used to alert

vehicle operator that the computerized engine control system has

detected a malfunction (when it stays on all the time with engine

running). On some models, the MIL may also be used to display trouble

codes.

         As a bulb and system check, malfunction indicator light will

glow when ignition switch is turned to ON position and engine is not

running. When engine is started, light should go out.

ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION 

1998 Mitsubishi Montero

         Engine Overhaul Procedures - General Information

         ALL PISTON ENGINES

         * PLEASE READ THIS FIRST *

         Examples used in this article are general in nature and do

not necessarily relate to a specific engine or system. Illustrations

and procedures have been chosen to guide mechanic through engine

overhaul process. Descriptions of processes of cleaning, inspection,

assembly and machine shop practice are included.

         Always refer to appropriate engine overhaul article in the

ENGINES section for complete overhaul procedures and specifications

for the vehicle being repaired.

         ENGINE IDENTIFICATION

         The engine may be identified from its Vehicle Identification

Number (VIN) stamped on a metal tab. Metal tab may be located in

different locations depending on manufacturer. Engine identification

number or serial number is located on cylinder block. Location varies

with manufacturer.

         INSPECTION PROCEDURES

         * 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.

         GENERAL

         Engine components must be inspected to meet manufacturer’s

specifications and tolerances during overhaul. Proper dimensions and

tolerances must be met to obtain proper performance and maximum engine

life.

         Micrometers, depth gauges and dial indicator are used for

checking tolerances during engine overhaul. Magnaflux, Magnaglo, dye-

check, ultrasonic and x-ray inspection procedures are used for parts

inspection.

         MAGNETIC PARTICLE INSPECTION

         Magnaflux & Magnaglo

         Magnaflux is an inspection technique used to locate material

flaws and stress cracks. The part in question is subjected to a strong

magnetic field. The entire part, or a localized area, can be

magnetized. The part is coated with either a wet or dry material that

contains fine magnetic particles.

         Cracks which are outlined by the particles cause an

interruption in the magnetic field. The dry powder method of Magnaflux

can be used in normal light. A crack will appear as an obvious bright

line.

         Fluorescent liquid is used in conjunction with a blacklight

in a second Magnaflux system called Magnaglo. This type of inspection

demands a darkened room. The crack will appear as a glowing line in

this process. Both systems require complete demagnetizing upon