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Isuzu engine C22NE / 22LE / 20LE. Manual - part 66

DRIVEABILITY AND EMISSIONS 6E1-93

Rough, Unstable, or incorrect Idle, Stalling Sympton (For Closed Loop System)

Step

Action

Value(s)

Yes

1. Reconnect the fuel pump relay.

2. Disconnect the fuel pump electrical connector at the

fuel tank.

3. Using a test light connected to ground, probe the fuel

pump feed wire (harness side).

4. Command the fuel pump ON with a scan tool.

Did the light illuminate for 2 seconds?

Go to Step 15

Go to Step 13

1. Honk the horn to verify that horn relay is functioning.

2. Susbstitute the horn relay for the fuel pump relay.

3. Leave the test light connected as in step 12.

4. Command the fuel pump ON with the scan tool.

Did the test light illuminate for 2 seconds when the fuel

pump was commanded ON?

Go to Step 17

Go to Step 14

1. Re-connect the horn relay in its proper location.

2. Check for a short circuit, blown fuse or open circuit

between the relay and the fuel tank.

Is the action complete?

Verify repair

1. with the fuel pump electrical connector at the fuel tank

disconnected, connect a test light between the feed

wire and the ground wire (harness side).

2. Command the fuel pump ON with a scan tool.

Did the test light illuminate for 2 seconds.

Go to Step 18

Go to Step 16

Repair the open circuit in the fuel pump ground wire.

Is the action complete?

Verify repair

1. Re-connect the horn relay in its proper location.

2. Replace the fuel pump relay.

Is the action complete?

Verify repair

Replace the fuel pump.

Is the action complete?

Verify repair

6E1-94 DRIVEABILITY AND EMISSIONS

Idle CO Concentration Check and

adjustment

Before starting adjusting work, check and confirm the
following conditions.
Normal engine operating temperature.
All accessories switched off.
Throttle valve closed.
Transmission in neutral.

Before starting adjusting work, step on accelerator pedal
a few times and do racing up to 3000rpm.

After taking foot off accelerator pedal, short out pins #5 +
#6 of ALDL Connector(Fixed under center console panel)
short.
(When you do this, Check Engine Lamp will blink, and
engine rpm will rise to 100 to 1600rpm)

In this condition, connect CO meter with Tail Pig and
check CO value(%).

If CO value is within the range shown below, leave as it
is. If it is out of range, adjust I t by turning the screw of
CO Adjuster.
(After adjusting, confirm that CO value becomes stable.)

Note: After adjusting work is finished, apply the liquid gasket to

the CO adjuster screw. And after that, all conditions to
restore to former state.

Regulated range of CO concentration value:

1.0

+0.2

- 0.5

DRIVEABILITY AND EMISSIONS 6E1-95

Poor Fuel Economy Symptom

Step

Action

Value(s)

Yes

DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy

is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.

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

Check owner's driving habits.
• Is the A/C On full time (defroster mode ON)?
• Are tires at the correct pressure?
• Are excessively heavy loads being carried?
• Is acceleration too much, too often?

Go to Step 5

Go to Step 6

Review the items in Step 4 with the customer and advise

as necessary.

Is the action complete?

System OK

1. Visually/Physically check: Vacuum hoses for splits,

kinks, and improper connections and routing as shown

on the "Emission Control System schematics".

Was a problem found?

Verify repair

Go to Step 7

Remove and check the air filter element for dirt or for

restrictions.

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

of heavy deposits.

2. Is 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

Check for low engine coolant level.

Was a problem found?

Verify repair

Go to Step 10

Check for an incorrect or faulty engine thermostat.

Refer to Engine Cooling.

Was a problem found?

Verify repair

Go to Step 11

Check for low engine compression. Refer to Engine

Mechanical.

Was a problem found?

Verify repair

Go to Step 12

6E1-96 DRIVEABILITY AND EMISSIONS

Poor Fuel Economy Symptom (Cont'd)

Step

Action

Value(s)

Yes

Check for proper calibration of the speedometer.

Does the speed indicated on the speedometer closely

match the vehicle speed displayed on the Scan Tool?

Go to Step 14

Go to Step 13

Diagnose and repair the inaccurate speedometer condition

as necessary. Refer to Vehicle Speed Sensor in Electrical

Diagnosis.

Verify repair

Check the air intake system and the crankcase for air

leaks.

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

Go to Step 16

Perform the procedure in Fuel System Pressure Test.

Was the fuel pressure normal?

Contact

Technical

Assistance

Verify repair

Content .. 64 65 66 67 ..