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Isuzu engine C22NE / 22LE / 20LE. Manual - part 65

DRIVEABILITY AND EMISSIONS 6E1-89

Detonation/Spark Knock Symptom (Cont'd)

Step

Action

Value(s)

Yes

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

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.

Was the On-Board Diagnostic (OBD) System Check

performed?

Go to Step 2

Go to OBD

System

Check

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

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

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

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

Using a Scan Tool, monitor TP angle with the engine

idling.

Is the TP angle at the specified value and steady?

Go to Step 7

Refer to

Diagnostic

Trouble Code

21 for further

diagnosis

Check for proper ignition voltage output with the spark

tester (Use commercially available tool).

Was a problem found?

Verify repair

Go to Step 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

Check for a lose ignition coil ground.

Refer to Electrical Ignition System.

Was a problem found?

Verify repair

Go to Step 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

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

Perform the injector Coil/Balance Test.

Was a problem found?

Verify repair

Go to Step 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

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

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

Was the “On-Board Diagnostic (OBD) System Check”

performed?

Go to Step 2

Go to OBD

System

Check

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

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

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

Repair short or open battery feed to fuel pump relay.

Is the action complete?

Verify repair

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

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

Locate and repair open in the fuel pump relay ground

circuit.

Is the action complete?

Verify repair

Check for short or open between the ECM and the fuel

pump relay.

Was a problem found?

Verify repair

Go to Step 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

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

Content .. 63 64 65 66 ..