engine ISUZU TROOPER 1995 Manual Online

6-6 ENGINE DIAGNOSIS
ROUGH ENGINE RUNNING
Complaint
Faulty parts Possible cause Correction
Engine misfires Ignition coil
Coil layer shorted Replace
regularly
high-tension Primary lead wire broken leakage due
Correct cables to defective insulator
Spark plugs
Fouling Clean
or install hotter type
plug
Insulator
nose leaking Replace
Fuel
injectors Fuel injector(s) defective Replace
Dropping register defective Replace
Engine Control
Faulty Replace
Module
Engine knocks Spark plugs
Spark plugs running too hot Install colder type spark
regularly
plugs
Engine Control Faulty
Replace
Module
Engine lacks Spark plugs
Fouled Clean
power Multipart Fuel
Fuel injectors defective Replace
Injection Manifold Absolute Pressure (MAP)
Correct or replace system Sensor or Manifold Absolute Pressure
Sensor
circuit defective
Engine
Coolant Temperature Sensor or Correct or replace
Engine Coolant Temperature Sensor
circuit dcefective
Engine
Control Module faulty Replace
Intake
Air Temperature Sensor or Intake
Air Temperature Sensor circuit Correct or replace
defective
Throttle Position Sensor or Throttle Correct or replace
Position Sensor
circuit defective
Knock
Sensor or Knock Sensor circuits Correct or replace
defective (DOHC only)
Knock Sensor Module or Knock Sensor Correct or replace .
Module
circuits defective (DOHC only)
•

ENGINE DIAGNOSIS 6-7
HESITATION
Condition Possible cause Correction
Hesitation on Throttle
Position Sensor adjustment incorrect Replace
throttle
acceleration valve
assembly
Throttle Position Sensor circuit open
or shorted Correct
or replace
Excessive play in accelerator linkage
Adjust or replace
Manifold Absolute
Pressure (MAP) Sensor circuit open or shorted Correct or replace
MAP Sensor defective Replace
Intake Air
Temperature (IAT) Sensor circuit open or shorted Correct or replace
Knock Sensor
(KS) Circuit open or shorted (DOHC only) Correct or replace
KS defective (DOHC only) Replace
KS Module circuits open or shorted (DOHC only) Correct or replace
KS Module defective (DOHC only) Replace
IAT Sensor defective Replace
Hesitation at
Fuel pressure
too low
high speeds
Fuel tank strainer clogged Clean or replace
Fuel pipe clogged
Clean or replace
Fuel filter clogged
Replace
Defective fuel
pump system Check and replace
Fuel Pressure Control Valve leaking Replace
Fuel injector
not working normally
Power supply or ground circuit for Multipart Fuel Injection Check and correct or
System shorted or open
replace
Distributor defective Replace
Cable of Multipart Fuel Injection System disconnected or defective Correct or replace
Engine Control Module defective Replace
Throttle Position Sensor circuit open
or shorted Correct or replace
Throttle Position Sensor defective Replace
Engine Coolant Temperature Sensor circuit open
or shorted Correct or replace
Engine Coolant Temperature Sensor defective Replace
MAP Sensor cable open
or shorted Correct or replace
MAP Sensor defective
Replace
IAT Sensor circuit open or shorted
Correct or replace
IAT Sensor defective Replace
KS Circuit open or shorted (DOHC only)
Correct or replace
KS defective (DOHC only) Replace
KS Module circuit open or shorted (DOHC only) Correct or replace
KS Module defective (DOHC only) Replace
Throttle valve
not wide opened
Check and correct or
replace
Air Cleaner Filter clogged
Replace filter element
Power supply voltage
too low Check and correct or
replace

6-8 ENGINE DIAGNOSIS
ENGINE LACKS POWER
Condition
Possible cause Correction
Trouble in fuel system Fuel Pressure Control Valve not Replace
working normally
Fuel
injector clogged Clean or replace
Fuel
pipe clogged Clean
Fuel filter clogged
or fouled Replace
Fuel
pump drive circuit not working Correct or replace
normally
Fuel tank not sufficiently breathing due Clean or replace
to clogged Evaporative Emission
Control System circuit
Water in
fuel system Clean
Inferior quality fuel
in fuel system Use fuel of specified octane
rating
Engine
Control Module supplied poor Correct circuit
voltage
Throttle
Position Sensor cable Correct or replace
disconnected or broken
Throttle Position Sensor defective Replace
Manifold Absolute
Pressure Sensor not Replace
working normally
Intake Air Temperature Sensor not Replace
working normally
Engine Coolant Temperature Sensor Correct or replace
circuit open or shorted
Engine
Coolant Temperature Sensor Replace
defective
Engine
Control Module defective Replace
Trouble
in intake or exhaust Air Cleaner Filter clogged Replace filter element
system Trouble in Induction air control valve Correct or replace
system (DOHC)
Air duct kinked or flattened Correct or replace
Ignition failure
Refer to Hard Start
Troubleshooting Guide
Heat range
of spark plug inadequate Install spark plugs of adequate
heat range
Electronic Ignition System with module Replace
•

ENGINE DIAGNOSIS 6-9
ENGINE LACKS POWER (Cont'd)
Condition Possible cause Correction
Engine overheating
Level of Engine Coolant too low Replenish
Thermo switch or fan motor defective Replace
Thermostat defective Replace
Engine
Coolant pump defective Correct or replace
Radiator clogged
Clean or replace
Radiator
filler cap defective Replace
Level
of oil in engine crankcase too low Change or replenish
or
wrong oil engine
Resistance in exhaust system
Clean exhaust system or
increased replace
defective parts
Throttle Position Sensor adjustment Adjust
Wide Open Throttle
incorrect switch setting
Throttle Position Sensor circuit open
or Correct or replace
shorted
Cylinder head gasket damaged Replace
Engine overcooling
Radiator
overcooling Install cover
in front of
radiator
Thermostat defective Replace
(Use a thermostat set
to open at a2·c (180.F))
Engine
lacks compression Refer to Hard Start
Others Tire inflation pressure
abnormal Adjust to recommend
pressures
Brake drag Adjust
Clutch slipping Adjust or replace
Level
of oil in engine crankcase too Correct level of engine oil
high
Exhaust Gas
Recirculation Valve Replace
defective
Back pressure transducer defective
Replace

6-10 ENGINE DIAGNOSIS
ENGINE
NOISY
Abnormal engine noise often consists of various noises originating in rotating parts, sliding parts and
other moving parts
of the engine. It is, therefore, advisable to locate the source of noise systematically.
Condition
Possible cause Correction
Noise from crank journals or Oil clearance increased due to worn Replace crank bearings and
from crank bearings
crank journals
or crank bearings crankshaft or regrind
(Faulty crank journals and
crankshaft and
install the over
crank bearings
usually make
size bearing
dull noise that becomes more Crankshaft out of round
Replace crank bearings and
evident when accelerating)
crankshaft
or regrind
crankshaft and
install the over
size bearing
Crank bearing seized Replace crank bearings and
crankshaft or regrind
crankshaft and
install the over
size bearing
Troubleshooting Procedure
Short out each spark plug in sequence using insulated sparkplug wire removers. Locate cylinder with
defective bearing by listening for abnormal noise that stops when spark plug is shorted out.
Condition
Possible cause Correction
Noise from connecting-rods or Bearing or crankshaft pin worn Replace connecting-rod
from connecting-rod bearings
bearings and crankshaft or
(Faulty connecting-rods or regrind-crankshaft and install
connecting-rod bearings
the over size bearing
usually make an abnormal
Crankpin out of round Replace
connecting-rod
noise slightly higher than the
bearings and crankshaft
or crank bearing noise, which regrind-crankshaft and install becomes more evident when the over size bearing
engine is accelerated)
Connecting-rod bent
Correct or replace
Connecting-rod bearing seized Replace
connecting-rod
bearings and crankshaft
or
regrind-crankshaft and install
the over size bearing
Troubleshooting Procedure
Abnormal noise stops when the spark plug on the cylinder with defective part is shorted out.
Condition
Possible cause Correction
Piston and cylinder Piston clearance increased due to Replace piston and cylinder
(Faulty piston or cylinder
cylinder
wear body
usually makes a combined Piston seized Replace piston and cylinder
mechanical thumping noise body which increases when engine Piston ring broken Replace piston and cylinder
is suddenly accelerated but
diminishes gradually as the body
engine warms up) Piston defective Replace pistons and others
Troubleshooting Procedure
Short out each spark plug and listen for change in engine noise.
Condition
Possible cause Correction
Piston pin noise Piston pin or piston pin hole worn Replace piston, piston pin and
(Piston makes noise each time connecting-rod assy
it goes up and down)
Troubleshooting Procedure
The slapping sound stops when spark plug on bad cylinder is shorted out.
•

ENGINE DIAGNOSIS 6-11
ENGINE NOISY (Cont'd)
Condition Possible cause Correction
Timing belt noise
Timing belt tension is incorrect Replace pusher or adjust the
ajust
pulley or replace timing
belt
Tensioner bearing defective Replace
Timing belt defective Replace
Timing wheels defective Replace
Timing belt comes in contact with Replace timing belt and timing
timing cover
cover
Valve noise Valve clearance incorrect Replace HLA
Valve and valve guide seized Replace valve and valve guide
Valve spring broken Replace
Valve
seat off-positioned
Correct
Crankshaft noise
Crankshaft end
play excessive (noise Replace thrust bearing
occurs
when clutch is engaged)
Engine knocking
Preignition due
to use of spark plugs of Install Spark Plugs of adequate
inadequate heat range
heat range
Carbon deposits in combustion
Clean
chambers
Fuel too low in octane rating Replace fuel
Wide Open Throttle enrichment system
Refer to Section 6E2
failure
Selection
of transmission gear incorrect Caution operator of incorrect
gear
selection
Engine overheating
Refer to "Engine Lacks Power"
Others Water
pump defective Replace
Drive belt slipping Adjust tension of drive belt or
replace drive belt

6-12 ENGINE DIAGNOSIS
ABNORMAL COMBUSTION
Condition
Possible cause Correction
Trouble in fuel Fuel pressure control valve defective Replace
injection system
Fuel filter clogged
Replace
Fuel pump clogged Clean or replace
Fuel tank
or fuel pipe clogged Clean or replace
Fuel injector clogged Clean or replace
Fuel
pump relay defective
Replace
Power supply cable for fuel pump loosely connected or Reconnect, correct or
defective
replace
Manifold Absolute
Pressure Sensor circuit open or shorted Correct or replace
Manifold Absolute
Pressure Sensor defective Replace
Engine Coolant Temperature
(ECT) Sensor circuit open or Correct or replace
shorted
ECT Sensor defective
Replace
Throttle
Position Sensor adjustment incorrect Replace throttle valve
Throttle
Position Sensor defective
Replace
Throttle
Position Sensor connector loosely connected Reconnect
Vehicle Speed Sensor cable loosely connected or Correct or replace
defective
Vehicle Speed Sensor loosely fixed Fix tightly
Vehicle Speed Sensor in wrong contact or defective Replace
Engine Control Module cable
loosely connected or Correct or replace
defective
Trouble in emission
Heated
Oxygen Sensor circuit open Correct or replace
control system
Heated
Oxygen Sensor defective Replace
Vacuum Switch
Valve (VSV); Replace
Exhaust Gas Recirculation defective
Signal vacuum hose loosely fitted or defective Correct or replace
Exhaust Gas Recirculation
Valve defective Replace
Back
Pressure Transducer defective Replace
ECT Sensor circuit open or shorted Correct or replace
ECT Sensor defective Replace
Pressure Control Valve (PCV) and hose clogged Correct or replace
Evaporator system
Refer
to Section 6E
Trouble in ignition
Refer to "Engine
system Lacks
Power"
Trouble in cylinder
Carbon deposits in combustion chamber Remove carbon
head parts
Carbon deposit on valve,
valve seat and valve guide
Remove carbon
•

ENGINE DIAGNOSIS 6-13
ENGINE OIL CONSUMPTION EXCESSIVE
Condition Possible cause Correction
Oil leaking
Oil pan drain plug loose Retighten or replace gasket
Oil pan setting bolts loosened Retighten
Oil pan gasket broken Replace gasket
Front cover retaining
bolts loose or Retighten or replace gasket
gasket broken
Head cover retaining
bolts loose or Retighten or replace gasket
gasket broken
Oil cooler adapter cracked Replace
Oil cooler
center bolt loose Retighten
Oil cooler 0-ring broken Replace
Oil cooler
piping loose or broken Retighten or replace
Oil filter
adapter cracked Replace
Oil filter
attachings bolt loose or rubber Retighten or replace oil filter
gasket broken
Oil cooler broken Replace
Crankshaft front or rear oil seal Replace oil seal
defective
Oil pressure unit loose or broken Retighten or replace
Blow-by
gas hose broken Replace hose
Positive Crankcase Ventilation
Valve
Clean
clogged
Engine/Transmisison coupling area Replace oil seal
Oil leaking
into combustion Valve stem oil seal defective Replace
chambers due to poor seal in Valve stem or valve guide worn Replace valve and valve guide valve system
Oil leaking into combustion
Cylinders and pistons worn excessively Rebore cylinder and replace
chambers
due to poor seal in pistons and others
cylinder parts
Piston ring gaps incorrectly positioned
Correct
Piston rings set
with wrong side up
Correct
Piston ring sticking Rebore
cylinder and replace
pistons and others
Piston rings and ring grooves
worn Replace pistons and others
Return ports in
oil rings clogged Clean piston
and replace rings
Crank case ventilation, Positive
Positive Crankcase Ventilation
Valve Clean
Crankcase Ventilation System clogged
malfunctioning
Others Improper oil viscosity
Use oil of recommended
S.A.E. viscosity
Continuous high speed driving
and/or Continuous high speed
servere usage such
as trailer towing operation and/or severe usage
will normally cause increased
oil consumption

6-14 ENGINE DIAGNOSIS
1;:-
FUEL CONSUMPTION EXCESSIVE
Condition
Possible cause Correction
Trouble in fuel system
Mixture too rich or too lean due to Refer to "Abnormal Combus-
trouble in fuel injection system tion"
Fuel cut function does not act Refer to "Abnormal Combus-
tion"
Trouble in ignition system
Misfiring or abnormal combustion due Refer to Hard Start or
to trouble in ignition system Abnormal Combustion
Troubleshooting Guide
Others Engine idle speed too high Reset Idle Air Control Valve
Returning
of accelerator control Correct
sluggish
Fuel system leakage
Correct or replace
Clutch slipping Correct
Brake drag Correct
Selection of transmission gear incorrect Caution operator of incorrect
gear selection
Excessive Exhaust
Gas Recirculation Refer to Abnormal
flow due to trouble in Exhaust Gas Combustion
Recirculation system
OIL PROBLEMS
Condition
Possible cause Correction
Oil pressure too low Wrong oil in use Replace with correct
engine
oil
Relief valve sticking Replace
Oil pump not operating
properly Correct or replace
Oil pump strainer clogged Clean or replace strainer
Oil pump worn Replace
Oil pressure gauge defective Correct or replace
Crankshaft bearing or connecting-rod Replace
bearing
worn
Oil contamination Wrong oil in use Replace with new engine
oil
Oil filter clogged Replace oil filter
Cylinder head gasket damage Replace
gasket
Burned gases leaking Replace piston and piston rings
or rebore cylinders
Oil not reaching valve system Oil passage in cylinder head or cylinder Clean or correct
body clogged
•

ENGINE DIAGNOSIS 6-15
MALFUNCTION INDICATOR LAMP
The instrument panei"CHECK ENGINE" Malfunction Indicator Lamp (MIL) illuminates by self diagnostic
system
when the system checks the bulb at the starting of engine, or senses malfunctions.
Complaint
Faulty parts
"CHECK
ENGINE" MIL
does not
illuminate
at the starting
of engine
"CHECK Heated Oxygen
ENGINE" MIL Sensor
illuminates,
and stays on
Engine
Coolant
Temperature Sensor
Throttle Position
Sensor
Crankshaft Position Sensor
Vehicle Speed
Sensor
Manifold
Absolute
Pressure Sensor
Intake Air
Temperature Sensor
Fuel Injector
ECM
Note: *1
-Random Access Memory
*2
-Read Only Memory
Possible cause Correction
Bulb defective Replace
MIL
circuit open Correct or replace
Command signal
circuit to operate self Correct or replace
diagnostic system shorted
Engine
Control Module (ECM) cable Correct or replace
loosely
connected, disconnected or
defective
ECM defective Replace
Deterioration of internal element Replace
Connector terminal improper contact Reconnect properly
Lead wire shorted Correct
Circuit
open Correct or replace
Deterioration of internal element Replace
Connector terminal improper contact Reconnect properly
Lead wire shorted Correct
Circuit
open Correct or replace
Open
or shorted circuits Correct or replace
Deterioration of sensor Replace
Open
or shorted circuit Correct or replace
Open
circuit Correct or replace
Open
or shorted circuit Correct or replace
Open
or shorted circuit Correct or replace
Open
or shorted circuit Correct or replace
Driver transistor defective Replace ECM
RAM*1 or ROM*2 malfunctioning Replace ECM