Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 374

6E–526

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Backfire Symptom

(Cont'd)

Step

No

Yes

Value(s)

Action

9

1. Check for the following engine mechanical

conditions.

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

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

Was a problem found?

—

Verify repair

Go to

Step 10

10

1. Check the intake and exhaust manifold(s) for

casting flash. Refer to

Engine Mechanical.

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 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–527

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Cuts Out, Misses Symptom

Step

Action

Value(s)

Yes

No

1

DEFINITION:
Steady pulsation or jerking that follows engine speed;
usually more pronounced as engine load increases.

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 14

Go to

Step 3

3

Was a visual/physical check performed?

—

Go to

Step 4

Go to

Visual/

Physical

Check

4

Was the “Electric Throttle Control (ETC) System
Check” performed?

—

Go to

Step 5

Go to

ETC

System

Check

5

1. Check the PCM grounds for clearness, tightness

and proper routing. Refer to the PCM wiring
diagrams in

Electrical Diagnosis.

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

Was a problem found?

—

Verify repair

Go to

Step 6

6

Observe the long term fuel trim on the Tech 2.

Is the long term fuel trim significantly in the negative
range (rich condition)?

—

Go to

Step 7

Go to

Step 8

7

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

Refer to

Diagnostic Aids in DTC P0172 Diagnostic

Support.

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

Was a problem found?

—

Verify repair

Go to

Step 10

8

Is the long term fuel trim significantly in the positive
range (lean condition)?

—

Go to

Step 9

Go to

Step 10

9

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

Refer to

Diagnostic Aids in DTC P0171 Diagnostic

Support.

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

Was a problem found?

—

Verify repair

Go to

Step 10

10

1. Check for incorrect idle speed. Ensure that the

following conditions are present:

D

The engine is fully warm.

D

The accessories are “off”.

2. Using a Tech 2, monitor the Engine Speed.

Is the Engine Speed within the specified values?

Desired Idle

Speed

Go to

Step 12

Go to

Step 11

6E–528

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Cuts Out, Misses Symptom

(Cont'd)

Step

No

Yes

Value(s)

Action

11

1. Visually/physically inspect for the following

conditions:

D

Restricted air intake system. Check for a
possible collapsed air intake duct, restricted
air filter element, or foreign objects blocking
the air intake system.

D

Large vacuum leak. Check for a condition that
causes a large vacuum leak, such as an
incorrectly installed or faulty PCV valve or
brake booster hose disconnected .

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

Was a problem found?

—

Verify repair

Go to

Step 9

12

Check the injector connections. If any of the injectors
are connected to an incorrect cylinder, correct as
necessary.

Was a problem found?

—

Verify repair

Go to

Step 13

13

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

Fuel

Metering System.

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

Was a problem found?

—

Verify repair

Go to

Step 14

14

1. Check for fuel in the pressure regulator vacuum

hose.

2. If fuel is present, replace the fuel pressure regulator

assembly. Refer to

Fuel Metering System.

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

Was a problem found?

—

Verify repair

Go to

Step 15

15

1. Check for proper ignition voltage output with spark

tester J 26792 (ST-125). Refer to

Electronic Ignition

System for the procedure.

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

Was a problem found?

—

Verify repair

Go to

Step 16

16

1. Remove spark plugs. Check for wet plugs, cracks,

wear, improper gap, burned electrodes, or heavy
deposits. Refer to

Electronic Ignition System.

NOTE: If spark plugs are gas or oil fouled, the cause of
the fouling must be determined before replacing the
spark plugs.

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

Was a problem found?

—

Verify repair

Go to

Step 17

17

1. Check for a loose ignition coil ground and ION

Sensing module circuit.

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

Was a problem found?

—

Verify repair

Go to

Step 18

18

1. Check ignition coils for cracks or carbon tracking.
2. If a problem is found, repair as necessary.

Was a problem found?

—

Verify repair

Go to

Step 19

19

Using a Tech 2, monitor the TP 1, 2 angle with the
engine idling.

Is the TP angle at the specified value and steady?

8

∼

10%

Go to

Step 20

Refer to

DTC

P0123 for

further

diagnosis

6E–529

6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Cuts Out, Misses Symptom

(Cont'd)

Step

No

Yes

Value(s)

Action

20

1. Check the PCV valve for proper operation. Refer to

Crankcase Ventilation System.

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

Was a problem found?

—

Verify repair

Go to

Step 21

21

1. Check the transmission range switch circuit. Use a

Tech 2 and be sure the Tech 2 indicates that the
vehicle is in drive with the gear selector in drive or
overdrive.

2. If a problem is found, diagnose and repair the

transmission range switch as necessary (refer to
4L30-E Automatic Transmission Diagnosis).

Was a problem found?

—

Verify repair

Go to

Step 22

22

1. Check 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

Worn rocker arms

D

Broken valve springs

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

Was a problem found?

—

Verify repair

Go to

Step 23

23

1. Check for faulty motor 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 24

24

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