Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 375
6E–530
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Hesitation, Sag, Stumble Symptom
Step
Action
Value(s)
Yes
No
1
DEFINITION:
Momentary lack of response as the accelerator is
pushed down. Can occur at any vehicle speed. Usually
most pronounced when first trying to make the vehicle
move, as from a stop sign. May cause the engine to stall
if severe enough.
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
Was the “Electric Throttle Control (ETC) System
Check” performed?
—
Go to
Step 3
Go to
ETC
System
Check
3
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 4
4
Was a visual/physical check performed?
—
Go to
Step 5
Go to
Visual/
Physical
Check
5
1. Check the fuel control heated oxygen sensors
(HO2S, B1S1 and B2S1). The fuel control heated
oxygen sensors (HO2S) should respond quickly to
different throttle positions. If they don’t, check them
for silicon or other contaminants from fuel or use of
improper RTV sealant. The sensors may have a
white powdery coating.
Silicon contamination causes a high but false
HO2S signal voltage (rich exhaust indication).
The PCM will then reduce the amount of fuel
delivered to the engine, causing a severe
driveability problem. For more information, refer
to
Powertrain Control Module (PCM) and Sensors.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 6
6
1. Check the fuel pressure. Refer to
Fuel System
Pressure Test.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 7
7
Observe the TP 1, 2 angle display on the Tech 2 while
slowly increasing accelerator pedal depression.
Does the TP angle display steadily increase from 8
∼
10% at closed throttle to 90
∼
92% at WOT?
—
Go to
Step 8
Go to
Step 9
8
Monitor 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 9
Go to
Step 10
9
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 11
6E–531
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Hesitation, Sag, Stumble Symptom
(Cont'd)
Step
No
Yes
Value(s)
Action
10
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 11
11
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 12
12
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 13
13
1. Check the 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 14
14
1. Remove spark plugs and 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 15
15
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 16
16
1. Check the MAF sensor connections.
2. If a problem is found, replace the faulty terminals as
necessary. Refer to
Electrical Diagnosis for wiring
repair procedures.
Was a problem found?
—
Verify repair
Go to
Step 17
6E–532
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Hesitation, Sag, Stumble Symptom
(Cont'd)
Step
No
Yes
Value(s)
Action
17
1. Visually/physically check vacuum hoses for splits,
kinks, and proper connections and routing as
shown on the “Vehicle Emission Control
Information” label.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 18
18
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–533
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Bank 1 Restricted Exhaust System Check
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
1. Remove the Bank 1 HO2S 2.
2. Install the Exhaust Backpressure Tester
(BT-8515-V or equivalent) in place of the Bank 1
HO2S 2.
3. Run the engine at normal operating temperature.
4. Increase the engine speed to 2000 RPM and allow
10 seconds for pressure to build.
5. Observe the exhaust system backpressure reading
on the gauge.
Does the reading exceed the amount in the value
column?
8.62 kPa
(1.25 psi)
Go to
Step 3
Go to
Step 4
3
Repair the restriction in the exhaust system after the
catalytic converter.
Possible faults include:
D
Collapsed pipe
D
Heat distress
D
Internal muffler failure
Is the action complete?
—
Verify repair
—
4
1. Install the Bank 1 HO2S 2.
2. Install the Exhaust Backpressure Tester in place of
Bank 1 HO2S 1.
3. Run the engine at normal operating temperature.
4. Increase the engine speed to 2000 RPM and allow
10 seconds for pressure to build.
5. Observe the exhaust system backpressure reading
on the gauge.
Does the reading exceed the amount in the value
column?
8.62 kPa
(1.25 psi)
Go to
Step 5
No trouble
found. If a
driveability
symptom
exists, refer
to symptom
charts
5
Repair the restriction in the catalytic converter.
Is the action complete?
—
Verify repair
—
NOTE: DTCs will be set by running the vehicle to normal
operating temperature after a cold start with the O2
sensor disconnected. After performing these tests, use
the Tech 2 to erase the DTCs that were set by the lack of
O2 sensor activity.
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