SECTION 6 - ENGINE DIAGNOSIS

Engine Diagnosis

Hard Starting

Engine Compression Test Procedure

Rough Engine Idling or Engine Stalling

Rough Engine Running

Hesitation

Engine Lacks Power

Engine Noisy

Abnormal Noise Due to Hydraulic Lash Adjustor

Troubleshooting Procedure

Abnormal Combustion

Engine Oil Consumption Excessive

Fuel Consumption Excessive

Oil Problems

Engine Oil Pressure Check

Malfunction Indicator Lamp

Techline

Engine Diagnosis

Hard Starting

1.Starting Motor Does Not Turn Over

Trouble Shooting Procedure

Turn on headlights and starter switch.

Condition Possible cause Correction

Headlights go out or dim

considerably

Battery run down or under

charged

Recharge or replace battery

Terminals poorly connected Clean battery posts and terminals

and connect properly

Starting motor coil circuit shorted Overhaul or replace

Starting motor defective Overhaul or replace

2.Ignition Trouble - Starting Motor Turns Over But Engine Does Not Start

Spark Test

Disconnect a high tension cable from any spark plug.

Connect the spark plug tester (use commercially

available tool), crank the engine, and check if a spark is

generated in the spark plug tester. Before cranking the

engine, make sure that the spark plug tester is properly

grounded. To avoid electrical shock, do not touch the

high tension cable while the engine is running.

Condition Possible cause Correction

Spark jumps across gap Spark plug defective Clean, adjust spark gap or replace

Ignition timing incorrect Refer to Ignition System

Fuel not reaching fuel injector(s)

or engine

Refer to item 3 (Trouble in fuel

system)

Valve timing incorrect Adjust

Engine lacks compression Refer to item 4 (Engine lacks

compression)

No sparking takes place Ignition coil disconnected or

broken

Connect properly or replace

Electronic Ignition System with

module

Replace

Poor connections in engine

harness

Correct

Engine Control Module cable

disconnected or defective

Correct or replace

Techline

3.Trouble in Fuel System

Condition Possible cause Correction

Starting motor turns over and

spark occurs but engine does not

start.

Fuel tank empty Fill

Water in fuel system Clean

Fuel filter clogged Replace filter

Fuel pipe clogged Clean or replace

Fuel pump defective Replace

Fuel pump circuit open Correct or replace

Evaporative Emission Control

system circuit clogged

Correct or replace

Multiport Fuel Injection System

faulty

Refer to "Electronic Fuel Injection"

section

4.Engine Lacks Compression

Condition Possible cause Correction

Engine lacks compression Spark plug loosely fitted or spark

plug gasket defective

Tighten to specified torque or

replace gasket

Valve timing incorrect Adjust

Cylinder head gasket defective Replace gasket

Valve incorrectly seated Lap valve

Valve stem seized Replace valve and valve guide

Valve spring weakened Replace

Cylinder or piston rings worn Overhaul engine

Piston ring seized Overhaul engine.

Engine Compression Test Procedure

1. Start and run the engine until the engine reaches

normal operating temperature.

2. Turn the engine off.

3. Remove all the spark plugs.

4. Remove ignition coil fuse (15A) and disable the

ignition system.

5. Remove the fuel pump relay from the relay and

fuse box.

6. Engage the starter and check that the cranking

speed is approximately 300 rpm.

7. Install cylinder compression gauge into spark

plug hole.

8. With the throttle valve opened fully, keep the

starter engaged until the compression gauge

needle reaches the maximum level. Note the

reading.

9. Repeat the test with each cylinder.

The pressure difference between the individual

cylinders should not exceed 100kPa (14.5 psi).

Rough Engine Idling or Engine Stalling

Condition Possible cause Correction

Trouble in fuel injection system Idle air control valve defective Replace

Throttle shutting off incomplete Correct or replace

Throttle position sensor circuit

open or shorted

Correct or replace

Fuel injector circuits open or

shorted

Correct or replace

Fuel injectors damaged Replace

Fuel pump relay defective Replace

Manifold Absolute Pressure

Sensor cable disconnected or

broken

Correct or replace

Manifold Absolute Pressure

Sensor defective

Replace

Engine Coolant Temperature

Sensor cable disconnected or

broken

Correct or replace

Engine Coolant Temperature

Sensor defective

Replace

Intake Air Temperature sensor

cable disconnected or broken

Correct or replace

Intake Air Temperature sensor

defective

Replace

Knock Sensor (KS) circuits open

or shorted

Correct or replace

KS defective Replace

KS Module circuits open or ground Correct or replace

KS Module defective Replace

Vehicle Speed Sensor circuit open

or shorted

Correct or replace

Vehicle Speed Sensor defective Replace

Trouble in emission control

system

Engine Control Module defective Replace

Canister purge solenoid circuit

open

Correct

Canister purge solenoid defective Replace

Evaporative Emission Canister

Purge control valve defective

Replace

Trouble in ignition system Refer to Hard Start

Troubleshooting Guide

Others Engine lacks compression Refer to Hard Start

Troubleshooting Guide

Valve incorrectly seated Lap valve

Air Cleaner Filter clogged Replace filter element

Valve timing incorrect Readjust

Idle air control valve broken Replace

Rough Engine Running

Condition Possible cause Correction

Engine misfires regularly Ignition coil layer shorted Replace

Spark plugs fouling Clean or install hotter type plug

Spark plug(s) insulator nose

leaking

Replace

Fuel injector(s) defective Replace

Engine control module faulty Replace

Engine knocks regularly Spark plugs running too hot Install colder type spark plugs

Powertrain control module faulty Replace

Engine lacks power Spark plugs fouled Clean

Fuel injectors defective Replace

Manifold Absolute Pressure (MAP)

Sensor or Manifold Absolute

Pressure Sensor circuit defective

Correct or replace

Engine Coolant Temperature

Sensor or Engine Coolant

Temperature Sensor circuit

defective

Correct or replace

Engine Control Module faulty Replace

Intake Air Temperature Sensor or

Intake Air Temperature Sensor

circuit defective

Correct or replace

Throttle Position Sensor or

Throttle Position Sensor circuit

defective

Correct or replace

Knock Sensor or Knock Sensor

circuits defective

Correct or replace

Knock Sensor Module or Knock

Sensor Module circuits defective

Correct or replace

Hesitation

Condition Possible cause Correction

Hesitation on acceleration Throttle Position Sensor

adjustment incorrect

Replace throttle 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

Correct or replace

KS defective Replace

KS Module circuits open or

shorted

Correct or replace

KS Module defective Replace

IAT Sensor defective Replace

Hesitation at high speeds

(Fuel pressure too low)

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

Hesitation at high speeds

(Fuel injector not working

normally)

Power supply or ground circuit for

Multiport Fuel Injection System

shorted or open

Check and correct or replace

Cable of Multiport Fuel Injection

System disconnected or defective

Correct or replace

Hesitation at high speeds 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 Correct or replace

KS defective Replace

KS Module circuit open or shorted Correct or replace

KS Module defective 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

Engine Lacks Power

Condition Possible cause Correction

Trouble in fuel system Fuel Pressure Control Valve not

working normally

Replace

Fuel injector clogged Clean or replace

Fuel pipe clogged Clean

Fuel filter clogged or fouled Replace

Fuel pump drive circuit not

working normally

Correct or replace

Fuel tank not sufficiently breathing

due to clogged Evaporative

Emission Control System circuit

Clean or replace

Water in fuel system Clean

Inferior quality fuel in fuel system Use fuel of specified octane rating

Engine Control Module supplied

poor voltage

Correct circuit

Throttle Position Sensor cable

disconnected or broken

Correct or replace

Throttle Position Sensor defective Replace

Manifold Absolute Pressure

Sensor not working normally

Replace

Intake Air Temperature sensor not

working normally

Replace

Engine Coolant Temperature

Sensor circuit open or shorted

Correct or replace

Engine Coolant Temperature

Sensor defective

Replace

Engine Control Module defective Replace

Trouble in intake or exhaust

system

Air Cleaner Filter clogged Replace filter element

Air duct kicked 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

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

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 stick Replace 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

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

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

Engine Oil Consumption Excessive

ConditionPossible causeCorrection

Oil leaking Oil pan drain plug loose Retighten or replace gasket

Oil pan setting bolds loosened Retighten

Oil pan gasket broken Replace gasket

Front cover retaining bolts loose or

gasket broken

Retighten or replace gasket

Head cover retaining bolts loose

or gasket broken

Retighten or replace gasket

Oil filter adapter cracked Replace

Oil filter attaching bolt loose or

rubber gasket broken

Retighten or replace oil filter

Crankshaft front or rear oil seal

defective

Replace oil seal

Oil pressure unit loose or broken Retighten or replace

Blow-by gas hose broken Replace hose

Engine/Transmission coupling

area

Replace oil seal

Oil leaking into combustion

chambers due to poor seal in

valve system

Valve stem oil seal defective Replace

Valve stem or valve guide worn Replace valve and valve guide

Oil leaking into combustion

chambers due to poor seal in

cylinder parts

Cylinders and pistons worn

excessively

Rebore cylinder and replace

pistons and others

Piston ring gaps incorrectly

positioned

Correct

Piston rings set with wrong side up Correct

Piston rings sticking Rebore cylinder and replace

pistons and others

Piston ring and ring groove worn Replace pistons and others

Return ports in oil rings clogged Clean piston and replace rings

Crank case ventilation, Positive

Crankcase Ventilation System

malfunctioning

Positive Crankcase Ventilation

Hose clogged

Clean

Others Improper oil viscosity Use oil of recommended S.A.E.

viscosity

Continuous high speed driving and

or severe usage such as trailer

towing

Continuous high speed operation

and or severe usage will normally

cause increased oil consumption

Fuel Consumption Excessive

ConditionPossible causeCorrection

Trouble in fuel systemMixture too rich or too lean due to

trouble in fuel injection system

Refer to "Abnormal Combustion"

Fuel cut function does not actRefer to "Abnormal Combustion"

Trouble in ignition systemMisfiring or abnormal combustion

due to trouble in ignition system

Refer to Hard Start or Abnormal

Combustion Troubleshooting

Guide

OthersEngine idle speed too highReset Idle Air Control Valve

Returning of accelerator control

sluggish

Correct

Fuel system leakageCorrect or replace

Clutch slippingCorrect

Brake dragCorrect

Selection of transmission gear

incorrect

Caution operator of incorrect gear

selection

Oil Problems

ConditionPossible causeCorrection

Oil pressure too lowWrong oil in useReplace with correct engine oil

Relief valve stickingReplace

Oil pump not operating properlyCorrect or replace

Oil pump strainer cloggedClean or replace strainer

Oil pump wornReplace

Oil pressure gauge defectiveCorrect or replace

Crankshaft bearing or connecting

rod bearing worn

Replace

Oil contaminationWrong oil in useReplace with new engine oil

Oil filter cloggedReplace oil filter

Cylinder head gasket damageReplace gasket

Burned gases leakingReplace piston and piston rings or

rebore cylinders

Oil not reaching valve systemOil passage in cylinder head or

cylinder body clogged

Clean or correct

Engine Oil Pressure Check

1.Check for dirt, gasoline or water in the engine

oil.

a.Check the viscosity of the oil.

b.Change the oil if the viscosity is outside the

specified standard.

c. Refer to the "Maintenance and Lubrication"

section of this manual.

2. Check the engine oil level.

The level should fall somewhere between the

"ADD" and the "FULL" marks on the oil level

dipstick.

If the oil level does not reach the "ADD" mark on

the oil level dipstick, engine oil must be added.

3. Remove the oil pressure unit.

4. Install an oil pressure gauge.

5. Start the engine and allow the engine to reach

normal operating temperature (About 80°C).

6. Measure the oil pressure.

Oil pressure should be:

150 kPa(21.8 psi) at idle speed.

7. Stop the engine.

8. Remove the oil pressure gauge

9. Install the oil pressure unit.

10. Start the engine and check for leaks.

Malfunction Indicator Lamp

The instrument panel "CHECK ENGINE" Malfunction

Indicator lamp (MIL) illuminates by self diagnostic

system when the system checks the starting of

engine, or senses malfunctions.

Condition Possible cause Correction

"CHECK ENGINE" MIL does not

illuminate at the starting of engine

Bulb defective Replace

MIL circuit open Correct or replace

Command signal circuit to operate

self diagnostic system shorted

Correct or replace

Engine Control Module (ECM)

cable loosely connected,

disconnected or defective

Correct or replace

ECM defective Replace

“CHECK ENGINE” MIL

illuminates, and stays on

Deterioration heated oxygen

sensor of internal element

Replace

Heated oxygen sensor connector

terminal improper contact

(If applicable)

Reconnect properly

Heated oxygen sensor lead wire

shorted (If applicable)

Correct

Heated oxygen sensor circuit open

(If applicable)

Correct or replace

Deterioration engine coolant

temperature sensor of internal

element

Replace

Engine coolant temperature

sensor connector terminal

improper contact

Reconnect properly

Engine coolant temperature

sensor lead wire shorted

Correct

Engine coolant temperature

sensor circuit open

Correct or replace

Throttle position sensor open or

shorted circuits

Correct or replace

Deterioration of crankshaft

position sensor

Replace

Crankshaft position sensor circuit

open or shorted

Correct or replace

Vehicle speed sensor circuit open Correct or replace

Manifold absolute pressure sensor

circuit open or shorted

Correct or replace

Intake air temperature sensor

circuit open or shorted

Correct or replace

Fuel injector circuit open or shorted Correct or replace

ECM driver transistor defective Replace EPROM or ECM

Malfunctioning of ECM RAM

(Random Access Memory) or

Malfunctioning of ECM PROM

(Programmed Read Only Memory)

Replace EPROM or ECM