Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 1674

6-8 ENGINE DIAGNOSIS (C24SE, C22NE, 22LE, 20LE)

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 filter cap defective

Replace

Level of oil in engine crankcase
too low or wrong oil in engine

Change or replenish

Resistance in exhaust system
increased

Clean exhaust system or replace
defective parts

Throttle Position Sensor
adjustment incorrect

Adjust Wide Open Throttle switch
setting

Throttle Position Sensor circuit
open or shorted

Correct or replace

Cylinder head gasket damaged

Replace

Cooling Fan clutch defective

Replace

Fan belt slipping

Adjust tension of V-belt or replace
V-belt

Engine overcooling

Thermostat defective

Replace (Use a thermostat set to
open at 92

°C (197.6°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 high

Correct level of engine oil

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 from
crank bearings
(Faulty crank journals and crank
bearings usually make dull noise
that becomes more evident when
accelerating)

Oil clearance increased due to
worn crank journals or crank
bearings

Replace crank bearings and
crankshaft or regrind crankshaft
and install the over size bearing

Crankshaft out of round

Replace crank bearings and
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

ENGINE DIAGNOSIS (C24SE, C22NE, 22LE, 20LE) 6-9

Abnormal Noise Due to Hydraulic Lash Adjuster

Should abnormal noise due to the hydraulic lash
adjuster trouble be heard immediately after the engine
is started, inspect as follows:

Condition

Possible cause

Correction

Abnormal noise is heard

Air contaminated

Bleed

HLA is spongy

Check ball valve broken

Repair

Safety valve in cylinder head
broken

Replace

Valve clearance is not zero

HLA inside stickReplace HLA assembly

Troubleshooting Procedure

Short out each spark plug in sequence using insulated
spark plug 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
from connecting rod bearings
(Faulty connecting rods or
connecting rod bearings usually
make an abnormal noise slightly
higher than the crank bearing
noise, which becomes more
evident when engine is
accelerated)

Bearing or crankshaft pin worn

Replace connecting rod bearings
and crankshaft or regrind
crankshaft and install the under
size bearing

Crankpin out of round

Replace connecting rod bearings
and crankshaft or regrind
crankshaft and install the under
size bearing

Connecting rod bent

Correct or replace

Connecting rod bearing seized

Replace connecting rod bearings
and crankshaft or regrind
crankshaft and install the under
size bearing

Troubleshooting Procedure

Abnormal noise stops when the spark plug on the

cylinder with defective parts is shorted out.

Condition

Possible cause

Correction

Piston and cylinder
(Faulty piston or cylinder usually
makes a combined mechanical
thumping noise which increases
when engine is suddenly
accelerated but diminishes
gradually as the engine warms up)

Piston clearance increased due to
cylinder wear

Replace piston and cylinder body

Piston seized

Replace piston and cylinder body

Piston ring broken

Replace piston and cylinder body

Piston defective

Replace pistons and others

6-10 ENGINE DIAGNOSIS (C24SE, C22NE, 22LE, 20LE)

Troubleshooting Procedure

Short out each spark plug and listen for change in

engine noise.

Condition

Possible cause

Correction

Piston pin noise
(Piston makes noise each time it
goes up and down)

Piston pin or piston pin hole worn

Replace piston, piston pin and
connecting rod assy

Troubleshooting Procedure

The slapping sound stops when spark plug on bad

cylinder is shorted out.

Condition

Possible cause

Correction

Timing belt noise

Timing belt tension is incorrect

Replace pusher or adjust the
tension pulley or replace timing
belt

Tensioner bearing defective

Replace

Timing belt defective

Replace

Timing wheels defective

Replace

Timing belt comes in contact with
timing cover

Replace timing belt and timing
cover

Valve noise

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 occurs when clutch is
engaged)

Replace thrust bearing

Engine knocking

Preignition due to use of spark
plugs of inadequate heat range

Install Spark Plugs of adequate
heat range

Fuel too low in octane rating

Replace fuel

Wide Open Throttle enrichment
system failure

Refer to Section 6E

Selection of transmission gear
incorrect

Caution operator or incorrect gear
selection

Engine overheating

Refer to "Engine Lacks Power"

Others

Water pump defective

Replace

V-belt slipping

Adjust tension of V-belt or replace
V-belt

ENGINE DIAGNOSIS (C24SE, C22NE, 22LE, 20LE) 6-11

Abnormal Combustion

Condition

Possible cause

Correction

Trouble in fuel injection system

Fuel pressure control valve
defective

Replace

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 defective

Reconnect, correct or 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
shorted

Correct or replace

ECT Sensor defective

Replace

Throttle Position Sensor
adjustment incorrect

Reconnect

Throttle Position Sensor defective

Replace

Throttle Position Sensor connector
loosely connected

Reconnect

Vehicle Speed Sensor cable
loosely connected or defective

Correct or replace

Vehicle Speed Sensor loosely
fixed

Fix tightly

Vehicle Speed Sensor in wrong
contact or defective

Replace

Engine Control Module cable
loosely connected or defective

Correct or replace

Trouble in emission control
system

Heated Oxygen Sensor circuit
open (If applicable)

Correct or replace

Heated Oxygen Sensor defective
(If applicable)

Replace

Signal vacuum hose loosely fitted
or defective

Correct or replace

ECT Sensor circuit open or
shorted

Correct or replace

ECT Sensor defective

Replace

Evaporative Emission Control
system (If applicable)

Refer to Section 6E

Trouble in ignition system

-

Refer to "Engine Lacks Power"

Trouble in cylinder head parts

Carbon deposits in combustion
chamber

Remove carbon

Carbon deposit on valve, valve
seat and valve guide

Remove carbon