Content .. 66 67 68 69 ..

Isuzu engine C22NE / 22LE / 20LE. Manual - part 68

DRIVEABILITY AND EMISSIONS 6E1-101

Cuts Out, Misses Symptom (Cont'd)

Step

Action

Value(s)

Yes

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 hoses or brake booster hose

disconnected.

Was a problem found?

Verify repair

Go to Step 11

1. Check the injector connections. If any of the injectors

are connected to an incorrect cylinder, correct as

necessary.

Was a problem found?

Verify repair

Go to Step 12

1. Perform the Injector Coil/Balance Test.

Was a problem found?

Verify repair

Go to Step 13

1. Check for fuel in the pressure regulator vacuum hose.

2. If fuel is present, replace the fuel pressure regulator

assembly.

Was a problem found?

Verify repair

Go to Step 14

Check for proper ignition voltage output with the spark

tester (Use commercially available tool).

Was a problem found?

Verify repair

Go to Step 15

1. Remove 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 16

Check for a loose ignition control module ground.

Was a problem found?

Verify repair

Go to Step 17

Using a Scan Tool, monitor the TP angle with the engine

idling.

Is the TP angle at the specified value and steady?

Go to Step 18

Refer to

Diagnostic

Trouble Code

21 for further

diagnosis

Check the PCV passage for proper operation.

Was a problem found?

Verify repair

Go to Step 19

6E1-102 DRIVEABILITY AND EMISSIONS

Cuts Out, Misses Symptom (Cont'd)

Step

Action

Value(s)

Yes

Check the following engine mechanical problems:
• Low compression
• Leaking cylinder head gasket
• Worn or incorrect camshaft
• Sticking or leaking valves
• Valve timing
• Broken valve springs
• Camshaft drive belt slipped or stripped.
Was a problem found?

Verify repair

Go to Step 20

Check for faulty motor mounts. Refer to Engine

Mechanical for inspection of mounts.

Was a problem found?

Verify repair

Go to Step 21

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

DRIVEABILITY AND EMISSIONS 6E1-103

Hesitation, Sag, Stumble Symptom

Step

Action

Value(s)

Yes

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

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?

Go to Step 4

Go to

Visual/Physic

al Check

1. Check the fuel control heated oxygen sensor (If

applicable). The HO2S should respond quickly to

different to throttle positions. If it doesn't, check for

silicon or other contaminants from fuel or use of

improper RTV sealant. The sensors may have a white

powdery coating. Silicon contamination sends a rich

exhaust signal which causes the ECM to command an

excessively lean air/fuel mixture.

Was a problem found?

Verify repair

Go to Step 5

Check the fuel pressure. Refer to Fuel System Pressure

Test.

Was a problem found?

Verify repair

Go to Step 6

Observe the "TP angle" display on the Scan Tool while

slowly increasing throttle pedal.

Does the TP angle display steadily increase from 0% at

closed throttle to 100% at WOT?

Go to Step 7

Go to Step 13

Monitor "Long Term Fuel Trim" on the Scan Tool.

Is the "Long Term Fuel Trim" in the negative range (rich

condition)?

Go to Step 8

Go to Step 9

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 10

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 10

Check for proper ignition voltage output with spark tester

(Use commercially available tool). Refer to Electronic

Ignition System for the procedure.

Was a problem found?

Verify repair

Go to Step 11

6E1-104 DRIVEABILITY AND EMISSIONS

Hesitation, Sag, Stumble Symptom (Cont'd)

Step

Action

Value(s)

Yes

Check for a loose ignition control module ground.

Was a problem found?

Verify repair

Go to Step 12

Visually/Physically inspect the secondary ignition wires.

Check for the following conditions.
• Verify that all ignition wire resistance are less than the

specified value.

• Value 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?

#1 cyl. 4.7k

Ω

#2 cyl. 3.9k

Ω

#3 cyl. 3.4k

Ω

#4 cyl. 3.1k

Ω

Verify repair

Go to Step 14

Replace the TP sensor.

Verify repair

1. Check the ignition coil secondary resistance.

2. Replace the coil if it is greater than the specified value.

Was a problem found?

2.5 k

Ω

Verify repair

Go to Step 15

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 16

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 17

Visually/Physically check the vacuum hoses for splits,

kinks and proper connections and proper connections and

routing as shown on the "Emission Control System

Schematics".

Was a problem found?

Verify repair

Go to Step 18

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.

3. If a problem is found, repair as necessary.

Was a problem found?

Verify repair

Contact

Technical

Assistance

Content .. 66 67 68 69 ..