Isuzu engine C22NE / 22LE / 20LE. Service manual — part 67
DRIVEABILITY AND EMISSIONS 6E1-97
Dieseling, Run-On Symptom
Step
Action
Value(s)
Yes
No
DEFINITION: Engine continues to run after key is turned OFF, but runs very rough. If engine runs smoothly, check
the ignition switch and adjustment.
1
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 the ignition feed
circuit.
Was a problem found?
-
Verify repair
Go to Step 5
5
1. Review all the diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
following:
• Visual/physical inspection.
• Scan Tool data.
• All electrical connections within a suspected circuit
and/or system.
Was a problem found?
-
Verify repair
Contact
Technical
Assistance
6E1-98 DRIVEABILITY AND EMISSIONS
Backfire Symptom
Step
Action
Value(s)
Yes
No
DEFINITION: Fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.
1
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
Check for proper ignition voltage output with the spark
tester (Use commercially available tool).
Was a problem found?
-
Verify repair
Go to Step 5
5
1. Remove the spark plugs and check for gas or oil
fouling cracks, wear, improper gap, burned electrodes
of heavy deposits.
2. If spark plugs are fouled, the cause of fouling must be
determined before replacing the spark plugs.
Was a problem found?
-
Verify repair
Go to Step 6
6
1. Visually/Physically inspect the secondary ignition wires.
Check for the following conditions:
• Verify that all ignition wire resistance are less than the
specified value.
• Verify that ignition wires are correctly routed to eliminate
cross-firing.
• Verify that ignition wires are not arcing to ground.
Spraying the secondary ignition wires with a light mist of
water may help locate an intermittent problem.
Was a problem found?
-
Verify repair
Go to Step 7
7
Check for an intermittent ignition system malfunction:
• Intermittent CKP 58X signal.
• Intermittent ignition feed circuit or sensor ground circuit
to the crankshaft position sensor.
Was a problem found?
-
Verify repair
Go to Step 8
8
Refer to Fuel System Diagnosis to determine if there is a
problem with fuel delivery.
Was a problem found?
-
Verify repair
Go to Step 9
9
Check for the following engine mechanical problems:
• Low compression
• Leaking cylinder head gasket
• Worn or incorrect camshaft
• Incorrect valve timing
• Sticking or leaking valves
• Camshaft drive belt slipped or stripped.
Was a problem found?
-
Verify repair
Go to Step 10
DRIVEABILITY AND EMISSIONS 6E1-99
Backfire Symptom (Cont'd)
Step
Action
Value(s)
Yes
No
10
Check the intake and exhaust manifold(s) for casting
flash. Refer to Engine Mechanical.
Was a problem found?
-
Verify repair
Go to Step 11
11
1. Review all the diagnostic procedures within this table.
2. If all procedures have been completed and no
malfunctions have been found, review/inspect the
following:
• Visual/physical inspection.
• Scan Tool data.
• All electrical connections within a suspected circuit
and/or system.
Was a problem found?
-
Verify repair
Contact
Technical
Assistance
6E1-100 DRIVEABILITY AND EMISSIONS
Cuts Out, Misses Symptom
Step
Action
Value(s)
Yes
No
DEFINITION: Steady pulsation or jerking that follows engine speed; usually more pronounced as engine load
increases.
1
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 the ECM grounds to verify that they are clean and
tight. Refer to the ECM wiring diagrams in Electrical
Diagnosis.
Was a problem found?
-
Verify repair
Go to Step 5
5
Monitor "02 Status" on the Scan Tool.
Is the "02 Status" in the rich condition (If applicable) ?
Go to Step 6
Go to Step 7
6
Check items that can cause the engine to run rich.
Refer to "Diagnostic Aids" in Diagnostic Trouble Code 45
(If applicable).
Was a problem found?
-
Verify repair
Go to Step 9
7
Is the "02 Status" significantly in the lean condition (If
applicable)?
-
Go to Step 8
Go to Step 9
8
Check items that can cause the engine to run lean.
Refer to Diagnostic Aids in Diagnostic Trouble Code 44 (If
applicable).
Was a problem found?
-
Verify repair
Go to Step 9
9
1. Check for incorrect idle speed. Ensure that the
following conditions are present:
• Engine fully warm.
• Accessories are OFF.
2. Using a Scan Tool, monitor the IAC position.
Is the IAC position within the specified values?
Between
5 and 50
counts
Go to Step 11
Go to Step 10
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