Isuzu Trooper (1998-2002 year). Manual - part 525

6E–470

6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS

Poor Fuel Economy Symptom

  (Cont'd)

Step

No

Yes

Value(s)

Action

10

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 11

11

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 12

12

1. Check the TCC operation.  Refer to 

4L30-E

Transmission Diagnosis.

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

Was a problem found?

—

Verify repair

Go to 

Step 13

13

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.

D

Check for a possible plugged three-way
catalytic converter by checking the exhaust
system back pressure.  Refer to 

Restricted

Exhaust System Check.

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

Was a problem found?

—

Verify repair

Go to 

Step 14

14

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 16

Go to 

Step 15

15

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

Vehicle Speed

Sensor in Electrical Diagnosis.

Was a problem found?

—

Verify repair

—

16

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 17

17

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 18

18

Perform the procedure in 

Fuel System Pressure Test.

Was the fuel pressure normal?

—

Contact

Technical

Assistance

Verify repair

6E–471

6VE1 3.5L 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?

—

Go to 

Step 13

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?

—

Go to 

Step 13

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

Go to 

Step 13

6

1. Check the fuel pressure.  Perform the procedure in

Fuel System Pressure Test.

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

Was a problem found?

—

Go to 

Step 13

Go to 

Step 7

7

1. Check for a faulty, plugged, or incorrectly installed

crankcase ventilation valve; also check the
crankcase ventilation system for plugging.

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

Was a problem found?

—

Go to 

Step 13

Go to 

Step 8

8

1. Check the injector connections.
2. If any of the injectors are  connected to an incorrect

cylinder, correct as necessary.

Was a problem found?

—

Go to 

Step 13

Go to 

Step 9

9

1. Perform the “Injector Coil/Balance Test” in 

Fuel

Metering System.

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

Was a problem found?

—

Go to 

Step 13

Go to 

Step 10

10

1. Refer to 

Engine Cooling for cooling system

diagnosis.

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

Was a problem found?

—

Go to 

Step 13

Go to 

Step 11

11

1. Check EVAP canister for fuel loading.  Refer to

Evaporative Emission Control System.

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

Was a problem found?

—

Go to 

Step 13

Go to 

Step 12

6E–472

6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS

Excessive Exhaust Emissions or Odors Symptom

  (Cont'd)

Step

No

Yes

Value(s)

Action

12

1. Remove excessive carbon buildup with a top engine

cleaner.  Refer to the instructions on the top engine
cleaner can.

2. Perform the exhaust emission test.

Does the vehicle pass the test?

—

System OK

Go to 

Step 14

13

Perform the exhaust emission test.

Does the vehicle pass the test?

—

System OK

Go to 

Step 14

14

Does the exhaust emission test indicate excessive CO
and HC levels or is long term fuel trim significantly in the
negative range (rich condition)?

—

Go to 

Step 15

Go to 

Step 16

15

1. Check items that can cause the engine to run rich.

Refer to 

Diagnostic Aids in DTC P0172 Diagnostic

Support.  Make any necessary repairs.

2. Perform the exhaust emission test.

Does the vehicle pass the test?

—

System OK

Go to 

Step 17

16

1. Check items that can cause the engine to run lean.

Refer to 

Diagnostic Aids in DTC P0171 Diagnostic

Support.  Make any necessary repairs.

2. Perform the exhaust emission test.

Does the vehicle pass the test?

—

System OK

Go to 

Step 17

17

1. Check the EGR system (refer to 

DTC P0401).

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

Was a problem found?

—

Go to 

Step 13

Go to 

Step 18

18

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?

—

Go to 

Step 13

Go to 

Step 19

19

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

6E–473

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Dieseling, Run-On Symptom

 

Step

Action

Value(s)

Yes

No

1

DEFINITION:
Engine continues to run after key is turned “OFF,” but
runs very rough.  If engine runs smooth, check ignition
switch and adjustment.

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

1. Check for a short between B+ and any of the ignition

feed circuits.

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

Was a problem found?

—

Verify repair

Go to 

Step 5

5

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