Isuzu Trooper (1998-2002 year). Manual - part 634

6E–184

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Rough, Unstable, or Incorrect Idle, Stalling Symptom

  (Cont'd)

Step

No

Yes

Value(s)

Action

9

1. Check for the following engine mechanical items.

Refer to 

Engine Mechanical for diagnosis

procedures:

D

Low compression

D

Sticking or leaking valves

D

Worn camshaft lobe(s)

D

Camshaft drive belt slipped or stripped

D

Incorrect valve timing

D

Valves clearance

D

Broken valve springs

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 10

10

1. Check for faulty engine mounts.  Refer to 

Engine

Mechanical for inspection of mounts.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 11

11

1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no

malfunctions have been found, review/inspect the
following:

D

Visual/physical inspection

D

Tech 2 data

D

Freeze Frame data/Failure Records buffer

D

All electrical connections within a suspected
circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Contact

Technical

Assistance

6E–185

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Poor Fuel Economy Symptom

 

Step

Action

Value(s)

Yes

No

1

DEFINITION:
Fuel economy, as measured by an actual road test, is
noticeably lower than expected.  Also, economy is
noticeably lower than it was on this vehicle at one time,
as previously shown by an actual road test. (Larger than
standard tires will cause odometer readings to be
incorrect, and that may cause fuel economy to appear
poor when it is actually normal.)

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to 

Step 2

Go to 

OBD

System

Check

2

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

—

Verify repair

Go to 

Step 3

3

Was a visual/physical check performed?

—

Go to 

Step 4

Go to 

Visual/

Physical

Check

4

Check owner’s driving habits.

D

Is the A/C “ON” full time (defroster mode “ON”)?

D

Are tires at the correct pressure?

D

Are excessively heavy loads being carried?

D

Is acceleration too much, too often?

D

Is engine oil correct?

Was a problem found?

—

Go to 

Step 5

Go to 

Step 6

5

Review the items in Step 4 with the customer and
advise as necessary.

Is the action complete?

—

System OK

—

6

1. Visually/physically check:  Vacuum hoses for splits,

kinks, and improper connections and routing as
shown on the “Vehicle Emission Control
Information” label.

2. If a problem is found, repair as necessary.

Was a repair required?

—

Verify repair

Go to 

Step 7

7

1. Remove and check the air filter element for dirt or for

restrictions. Refer to 

Air Intake System.

2. Replace the air filter element if necessary.

Was a repair required?

—

Verify repair

Go to 

Step 8

8

1. Check for low engine coolant level.  Refer to 

Engine

Cooling.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 9

9

1. Check for an incorrect or faulty engine thermostat.

Refer to 

Engine Cooling.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 10

10

1. Check for low engine compression.  Refer to 

Engine

Mechanical.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 11

6E–186

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Poor Fuel Economy Symptom

  (Cont'd)

Step

No

Yes

Value(s)

Action

11

1. Check the TCC operation.  Refer to 

Transmission

Diagnosis.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 12

12

1. Check the exhaust system for possible restriction:

D

Inspect the exhaust system for damaged or
collapsed pipes.

D

Inspect the muffler for heat distress or possible
internal failure.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 13

13

Check for proper calibration of the speedometer.

Does the speed indicated on the speedometer closely
match the vehicle speed displayed on the Tech 2?

—

Go to 

Step 15

Go to 

Step 14

14

Diagnose and repair an inaccurate speedometer
condition as necessary.  Refer to 

Vehicle Speed

Sensor in Electrical Diagnosis.

Was a problem found?

—

Verify repair

—

15

1. Check the air intake system and the crankcase for

air leaks.  Refer to 

Air Intake System and

Crankcase Ventilation System.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 16

16

1. Review all diagnostic procedures within this table.
2. When all procedures have been completed and no

malfunctions have been found, review/inspect the
following:

D

Visual/physical inspection

D

Tech 2 data

D

Freeze Frame data/Failure Records buffer

D

All connections within a suspected circuit
and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 17

17

Perform the procedure in 

Injector Test.

Was the fuel pressure normal?

—

Contact

Technical

Assistance

Verify repair

6E–187

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Excessive Exhaust Emissions or Odors Symptom

 

Step

Action

Value(s)

Yes

No

1

DEFINITION:
Vehicle fails an emission test.  Vehicle has excessive
“rotten egg” smell. (Excessive odors do not necessarily
indicate excessive emissions.)

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to 

Step 2

Go to 

OBD

System

Check

2

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,

correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

—

Verify repair

Go to 

Step 3

3

Was a thorough visual/physical check performed?

—

Go to 

Step 4

Go to 

Visual/

Physical

Check

4

1. Check for vacuum leaks.  Check vacuum lines,

intake manifold, throttle body, etc.

2. If a problem is found, repair as necessary.

Were any vacuum leaks located?

—

Verify repair

Go to 

Step 5

5

1. Check the fuel cap for proper installation.
2. Secure the fuel cap if necessary.

Was the fuel cap installed properly?

—

Go to 

Step 6

Verify repair

6

1. Injector Test

Operate the each injector by Tech 2 with the
ignition “ON” and check if the working noise
confirm.

2. If a problem is found, check the harness or replace

the injector.

Is the action complete?

—

Verify repair

Go to 

Step 7

7

1. Refer to 

Engine Cooling for cooling system

diagnosis.

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 8

8

1. Check for an engine mechanical problem.

Perform a cylinder compression check (Refer to
Engine Mechanical).

2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to 

Step 9

9

1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no

malfunctions have been found, review/inspect the
following:

D

Visual/physical inspection

D

Tech 2 data

D

Freeze Frame data/Failure Records butter

D

All electrical connections within a suspected
circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Contact

Technical

Assistance