Isuzu engine C22NE / 22LE / 20LE. Service manual — part 65
DRIVEABILITY AND EMISSIONS 6E1-89
Detonation/Spark Knock Symptom (Cont'd)
Step
Action
Value(s)
Yes
No
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:
• 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
6E1-90 DRIVEABILITY AND EMISSIONS
Rough, Unstable, or Incorrect Idle, Stalling Symptom (For Open Loop System)
Step
Action
Value(s)
Yes
No
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary
in RPM. Either condition may be severe enough to stall the engine.
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, including the
rotor, ignition coil and secondary ignition wires?
-
Go to Step 4
Go to
Visual/Physic
al Check
4
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 IAC position.
Is the IAC position within the specified values?
Between 8
and 50
counts
Go to Step 7
Go to Step 5
5
1. Visually/Physically inspect for the following conditions:
• Restricted air intake system. Check for a restricted
air filter element, or foreign objects blocking the air
intake system.
• Check for objects blocking the IAC passage or
throttle bore, excessive deposits in the IAC passage
and on the IAC pintle, and excessive deposits in the
throttle bore and on the throttle plate.
• Check for a condition that causes a large vacuum
leak, such as an incorrectly installed or faulty
crankcase ventilation hose/brake booster hose.
Was a problem found?
-
Verify repair
Go to Step 6
6
Using a Scan Tool, monitor TP angle with the engine
idling.
Is the TP angle at the specified value and steady?
0%
Go to Step 7
Refer to
Diagnostic
Trouble Code
21 for further
diagnosis
7
Check for proper ignition voltage output with the spark
tester (Use commercially available tool).
Was a problem found?
-
Verify repair
Go to Step 8
8
1. Remove the spark plugs and check for gas or oil
fouling cracks, wear, improper gap, burned electrodes,
heavy deposits or improper heat range
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 9
DRIVEABILITY AND EMISSIONS 6E1-91
Rough, Unstable, or Incorrect Idle, Stalling Symptom (For Open Loop System)
Step
Action
Value(s)
Yes
No
9
Check for a lose ignition coil ground.
Refer to Electrical Ignition System.
Was a problem found?
-
Verify repair
Go to Step 10
10
Check the items that can cause the engine to run lean.
Refer to Idle CO Concentration Check and Adjustment.
Was a problem found?
-
Verify repair
Go to Step 11
11
Check the injector connections, if any of the injectors are
connected an incorrect cylinder, correct as necessary.
Was a problem found?
-
Verify repair
Go to Step 12
12
Perform the injector Coil/Balance Test.
Was a problem found?
-
Verify repair
Go to Step 13
13
Check the following engine mechanical problems:
Low compression
Leaking cylinder head gasket
Worn or incorrect camshaft
Sticking or leaking valves
Broken valve springs
Camshaft drive belt slipped or stripped
Was a problem found?
-
Verify repair
Go to Step 14
14
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 15
15
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
6E1-92 DRIVEABILITY AND EMISSIONS
Rough, Unstable, or incorrect Idle, Stalling Sympton (For Closed Loop System)
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. Read the “Caution” above.
2. Relieve the fuel system pressure and install the fuel
pump pressure gauge to the test fitting.
3. Use a scan tool to command the fuel pump ON.
Is there an immediate pressure build-up which indicates
the pump is running?
-
Go to Step 3
Go to Step 4
3
1. Verify that the pump is not running by removing the
fuel filler cap and listening.
2. Command the pump ON with the scan tool.
Did the pump turn OFF after 2 seconds?
-
Test
completed
Go to Step 12
4
1. Ignition OFF.
2. Remove the fuel pump relay.
3. Using a test light connected to ground, probe the
battery feed to the relay.
Did the light illuminate?
-
Go to Step 6
Go to Step 5
5
Repair short or open battery feed to fuel pump relay.
Is the action complete?
-
Verify repair
-
6
1. Connect a test light between the two wires that
connect to the fuel pump relay pull-in coil.
2. Ignition ON.
Did the test light illuminate for 2 seconds and then turn
off?
-
Go to Step 12
Go to Step 7
7
1. With a test light connected to battery (-), probe the fuel
pump relay connector at the wire which runs from the
relay pull-in coil to the ECM.
2. Ignition ON.
Did the test light illuminate for 2 seconds and then turn
off?
-
Go to Step 8
Go to Step 9
8
Locate and repair open in the fuel pump relay ground
circuit.
Is the action complete?
-
Verify repair
-
9
Check for short or open between the ECM and the fuel
pump relay.
Was a problem found?
-
Verify repair
Go to Step 10
10
1. Check the fuel pump relay circuit for a poor terminal
connection at the ECM.
2. If a problem is found, replace terminal as necessary.
Was a problem found?
-
Verify repair
Go to Step 11
11
Replace the ECM.
Important: The replacement ECM must be programmed.
Refer to On-Vehicle Service in Powertrain Control Module
and Sensors for procedures.
Is the action complete?
-
Verify repair
-
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