Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 92

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–363

LACK OF POWER, SLUGGISH OR SPONGY SYMPTOM

DEFINITIONS: Engine delivers less than expected power. Attempting part-throttle acceleration results in little or no
increase in vehicle speed.

Step

Action

Value(s)

Yes

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

—

Go to Step 2

Go to On Board

Diagnostic

(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 visually/physical check performed?

—

Go to Step 4

Go to Visual /

physical Check

Is the customer using the incorrect fuel type?

Diesel fuel

only

Replace with

diesel fuel

Go to Step 5

Visually/physically inspect for the following conditions.

• Restrict air intake system. Check for a restricted air

filter element, or foreign objects blocking the air
intake system

• Check for objects blocking or 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.

• Restrict air intake system at the turbocharger.

Check for objects blocking the turbocharger
compressor wheel or turbine shaft sticking.

If a problem is found, repair as necessary.
Was a problem found?

—

Verify repair

Go to Step 6

Check the ECM & PSG grounds to verify that they are
clean and tight. Refer to the ECM wiring diagrams.
Was a problem found?

—

Verify repair

Go to Step 7

1. Using the Tech 2, display the ECT sensor and IAT

sensor value.

2. Check the displayed value.

Does the Tech 2 indicate correct temperature
depending on engine condition?
If a problem is found, repair as necessary.
Was the problem found?

—

Verify repair

Go to Step 8

1. Using the Tech 2, display the FT sensor value.

2. Check the displayed value.

Does the Tech 2 indicate correct temperature
depending on engine condition?
If a problem is found, repair as necessary.
Was the problem found?

—

Go to Step 30

Go to Step 9

1. Using the Tech 2, ignition “On” and engine “Run”.

2. Monitor the “Mass Air Flow” in the data display.

Does the Tech 2 indicate correct “Mass Air Flow”
depending on accelerator pedal operation?

—

Go to Step 14

Go to Step 10

6E–364

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

Remove the MAF & IAT sensor assembly and check
for the following conditions.

• Objects blocking at the MAF sensor element.
If a problem is found, repair as necessary.
Was the problem found?

—

Verify repair

Go to Step 11

Check the MAF sensor harness for the following
conditions.

• Check for poor connector connection.

• Check for misrouted harness.

• Check for any accessory parts which may cause

electric interference.

If a problem is found, repair as necessary.
Was a problem found?

—

Verify repair

Go to Step 12

Substitute a known good MAF & IAT sensor assembly
and recheck.
Was the problem solved?

—

Go to Step 13

Go to Step 30

Replace the MAF & IAT sensor assembly.
Is the action complete?

—

Verify repair

—

1. Using the Tech 2, ignition “On” and engine “Off”.

2. Monitor the “Pedal/Throttle Position” and “Idle

Switch” in the data display.

Does the Tech 2 indicate correct “Pedal/Throttle
Position” from 0% to 100% and correct “Idle Switch”
status depending on accelerator pedal operation?

—

Go to Step 19

Go to Step 15

1. Using the Tech 2, ignition “On” and engine “Off”.

2. Monitor the “Pedal/Throttle Position” and “Idle

Switch” in the data display.

3. Adjust the accelerator cable or TPS within 0% to

100%.

Was the problem solved?

—

Verify repair

Go to Step 16

Check the TPS harness for the following conditions.

• Check for poor connector connection.

• Check for misrouted harness.

• Check for any accessory parts which may cause

electric interference.

If a problem is found, repair as necessary.
Was a problem found?

—

Verify repair

Go to Step 17

Substitute a known good TPS and recheck.
Was the problem solved?

—

Go to Step 18

Go to Step 30

Replace the TPS.
Is the action complete?

—

Verify repair

—

Step

Action

Value(s)

Yes

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–365

1. Using the Tech 2 and ignition “On” and engine

“Run”.

2. Monitor the following parameters in the data

display.

• “Desired Injection Quantity” & “Injection Quantity”

• “Desired Injection Start” & “Actual Injection Start”

Are the large gap or unstable parameter displayed
between “Desired” and “Actual”?

—

Go to Step 23

Go to Step 20

Using the vacuum pump and check the EGR valve (if
equipped) operation for the following condition through
the small window.

• Restrict shaft movement. Check for objects sticking

the shaft, broken diaphragm or excessive carbon
deposit.

If a problem is found, repair as necessary.
Was a problem found?

—

Verify repair

Go to Step 21

Using the vacuum pump and check the exhaust
throttle valve (if equipped) operation for the following
condition.

• Restrict shaft movement. Check for objects sticking

the shaft, broken diaphragm or excessive carbon
deposit.

Was a problem found?

—

Verify repair

Go to Step 22

Step

Action

Value(s)

Yes

When idling or part-throttle When accelerated

High

Desired

Low

Time

Actual

High

Low

Desired

Actual

Time

Vacuum Pump

Small Window

6E–366

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

Check the exhaust system for a possible restriction.

• Damaged or collapsed pipes or catalytic converter.

• Internal muffler failure.
If a problem is found, repair as necessary.
Was a problem found?

—

Verify repair

Go to Step 23

Visually/physically inspect for the following conditions.

• Restrict fuel supply system. Check for a pinched

fuel hose/pipe.

• Check for a condition that causes fuel waxing or

icing, such as the customer is using an incorrect
fuel type in winter season or water mixed with the
fuel.

If a problem is found, repair as necessary.
Was a problem found?

—

Verify repair

Go to Step 24

Replace the fuel filter.
Was the problem solved?

—

Verify repair

Go to Step 25

Remove the eye bolt with gauze filter from the
injection pump and check for the following conditions.

• Objects blocking at the gauze filter. Check for a

condition that causes contaminated fuel, such as
the customer is using an aftermarket fuel filter or
extended maintenance interval.

• Check for a condition that causes fuel waxing or

icing, such as the customer is using an incorrect
fuel type in winter season or water mixed with the
fuel.

If a problem is found, repair as necessary.
Was the problem found?

—

Replace the eye

bolt with gauze

filter and verify

repair

Go to Step 26

Step

Action

Value(s)

Yes

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