Isuzu Trooper (1998-2002 year). Service manual — part 341
6E–277
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 12
Go to
Step 3
3
Was a thorough visual/physical check performed?
—
Go to
Step 4
Go to
Visual/Physic
al 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 12
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 12
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 12
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 12
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 12
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 12
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 12
Go to
Step 11
11
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 13
12
Perform the exhaust emission test.
Does the vehicle pass the test?
—
System OK
Go to
Step 13
6E–278
ENGINE DRIVEABILITY AND EMISSIONS
Excessive Exhaust Emissions or Odors Symptom
(Cont'd)
Step
No
Yes
Value(s)
Action
13
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 14
Go to
Step 15
14
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 16
15
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 16
16
1. Check the EGR system.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Go to
Step 12
Go to
Step 17
17
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 12
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–279
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/Physic
al 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
6E–280
ENGINE DRIVEABILITY AND EMISSIONS
Backfire Symptom
Step
Action
Value(s)
Yes
No
1
DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust
system, making a loud popping noise.
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/Physic
al Check
4
1. Check for proper ignition voltage coil output with
spark tester 5-8840-0383-0. Refer to
Electric
Ignition System for procedure.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 5
5
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. Refer to
DTC P0172 to determine the
cause of a rich condition or
Engine Mechanical for an oil
fouling condition.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 6
6
1. Visually/physically inspect the ignition coils for
cracks.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 7
7
1. Check for an intermittent ignition system
malfunction:
D
Intermittent CKP 58X signal.
D
Intermittent ignition feed circuit or sensor
ground circuit to the crankshaft position
sensor.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Go to
Step 8
8
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 9
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