Daewoo Nubira. Manual - part 120

1F – 364

I

ENGINE CONTROLS

DAEWOO V–121 BL4

LACK OF POWER, SLUGGISHNESS, OR SPONGINESS

The engine delivers less than expected power. There
is little or no increase in speed when the accelerator
pedal is partially applied.

Step

Action

Value(s)

Yes

No

1

Were the Important Preliminary Checks performed?

Go toStep 2

Go to”Impor-

tant Preliminary

Checks”

2

1.  Verify the customer’s complaint.
2.  Compare the performance of the customer’s

vehicle with a similar unit.

Does the problem exist?

Go toStep 3

System OK

3

1.  Inspect the air filter for excessive contamina-

tion.

2.  Replace the air filter as needed.
3.  Check the transaxle shift pattern and downshift

operation.

Does the transaxle operate properly?

Go toStep 4

Go toStep 5

4

Check the fuel system pressure.
Is the fuel system pressure within specifications?

41–47 psi

(284–325 kPa)

Go toStep 7

Go toStep 6

5

Repair the transaxle as needed.
Is the repair complete?

System OK

6

Repair the fuel system as needed.
Is the repair complete?

System OK

7

Check for a restricted fuel filter or contaminated fuel.
Is the problem found?

Go toStep 8

Go toStep 9

8

Repair or replace any components as needed.
Is the repair complete?

System OK

9

1.  Check the ignition system output for all of the

cylinders using a spark tester.

2.  Check for proper ignition control operation.

Is the ignition system operating properly?

Go toStep 10

Go toStep 11

10

1.  With the engine at normal operating tempera-

ture, connect a vacuum gauge to a vacuum
port on the intake manifold.

2.  Operate the engine at 1,000 rpm.
3.  Record the vacuum reading.
4.  Increase the engine speed to 2,500 rpm.
5.  Note the vacuum reading at a steady 2,500

rpm.

Does the vacuum decrease more than the value
specified?

10 kPa

(3 in. Hg)

Go toStep 12

Go toStep 15

11

Repair or replace any ignition system components
as needed.
Is the repair complete?

System OK

12

Inspect the exhaust system for restrictions and dam-
aged or collapsed pipes.
Is the problem found?

Go toStep 13

Go toStep 14

13

Repair or replace any components as needed.
Is the repair complete?

System OK

ENGINE CONTROLS  1F – 365

DAEWOO V–121 BL4

Step

No

Yes

Value(s)

Action

14

1.  Check the cylinder compression and valve tim-

ing.

2.  Inspect the camshaft for excessive wear.

Is the problem found?

Go toStep 15

Go toStep 16

15

Repair or replace any engine components as need-
ed.
Is the repair complete?

System OK

16

1.  Check the powertrain control module

(PCM)/engine control module (ECM) grounds
for being clean, tight, and in their proper loca-
tion.

2.  Check the Exhaust Gas Recirculation (EGR)

valve for being open or partially open all the
time.

3.  Check the Torque Converter Clutch (TCC) op-

eration.

4.  Check the A/C system operation.
5.  Check the generator output.
6.  Repair the generator if the output is not within

the specified range.

Are all checks and repairs complete?

12–16 v

System OK

 

DETONATION/SPARK KNOCK

Step

Action

Value(s)

Yes

No

1

Were the Important Preliminary Checks performed?

Go toStep 2

Go to”Impor-

tant Preliminary

Checks”

2

1.  Fill the fuel tank with a known good grade of

gasoline that has the octane rating of the value
specified.

2.  Reevaluate the vehicle’s performance.

Does the detonation problem still exist?

87–89 octane

Go toStep 3

System OK

3

1.  Inspect for low engine coolant.
2.  Check for restricted airflow to the radiator or

restricted coolant flow.

3.  Check for a faulty thermostat.
4.  Check for an incorrect coolant solution.

Is the problem found?

Go toStep 4

Go toStep 5

4

Repair or replace any cooling system components
as needed.
Is the repair complete?

System OK

5

1.  Check the voltage using the scan tool.
2.  Replace the Engine Coolant Temperature

(ECT) sensor if the resistance is not within
specifications as listed in the Diagnostic Aids
for diagnostic trouble code (DTC) P0118.

Is the problem found?

Go toStep 6

Go toStep 7

6

Replace the ECT sensor or repair the circuit as
needed.
Is the repair complete?

System OK

1F – 366

I

ENGINE CONTROLS

DAEWOO V–121 BL4

Step

No

Yes

Value(s)

Action

7

1.  Check the ignition system output with a spark

tester.

2.  Inspect the spark plugs for the proper heat

range and gap.

3.  Check for the proper operation of the ignition

controls.

Is the ignition system operating properly?

Go toStep 9

Go toStep 8

8

Repair or replace the ignition system components as
needed.
Is the repair complete?

System OK

9

1.  Connect the scan tool to the Data Link Con-

nector (DLC).

2.  Road test the vehicle at the speed of the com-

plaint.

3.  Monitor the long term fuel trim reading from the

scanner data stream.

Is the long term fuel trim reading above the value
specified?

150 counts

Go to”Diagnos-

tic Aids for

DTC P0171”

Go toStep 10

10

Check the fuel system pressure.
Is the problem found?

41–47 psi

(284–325 kPa)

Go toStep 11

Go toStep 12

11

Repair or replace the fuel system components as
needed.
Is the repair complete?

System OK

12

1.  Inspect for carbon buildup inside the engine.
2.  Remove the carbon with a top engine cleaner.

Follow the instructions supplied with the prod-
uct.

3.  Check the basic engine parts such as the cam-

shaft, the cylinder head, the pistons, etc. for
excessive wear.

4.  Replace any excessively worn parts.

Is the procedure complete?

Go toStep 13

13

1.  Check the Exhaust Gas Recirculation (EGR)

valve for proper operation.

2.  Check the air intake system for proper opera-

tion.

3.  Check the Torque Converter Clutch (TCC) op-

eration and transaxle shift points.

4.  Check the service bulletins for Programmable

Read–Only Memory (PROM) updates.

5.  Check the cylinder compression.
6.  Repair or replace any faulty components.

Are all checks and repairs complete?

System OK

 

ENGINE CONTROLS  1F – 367

DAEWOO V–121 BL4

HESITATION, SAG, STUMBLE

Involves a momentary lack of response as the
accelerator is pushed down. This can occur at any
vehicle speed. It is usually the most severe when first
trying to make the vehicle move, as from a stop.
Hesitation, sag, or stumble may cause the engine to

stall if severe enough.

Important : Before diagnosing this condition, check ser-
vice bulletins for Programmable Read–Only Memory
(PROM) updates.

Step

Action

Value(s)

Yes

No

1

Were the Important Preliminary Checks performed?

Go toStep 2

Go to”Impor-

tant Preliminary

Checks”

2

1.  Check the fuel system pressure. If the pres-

sure is not within the value specified, service
the fuel system as needed.

2.  Inspect the Throttle Position (TP) sensor for

binding or sticking. The TP sensor voltage
should increase at a steady rate as the throttle
is moved toward Wide Open Throttle (WOT).

Is the problem found?

41–47 psi

(284–325 kPa)

Go toStep 3

Go toStep 4

3

Repair or replace any components as needed.
Is the repair complete?

System OK

4

1.  Check the Manifold Absolute Pressure (MAP)

sensor response and accuracy.

2.  Inspect the fuel for water contamination.
3.  Check the Evaporative (EVAP) Emission canis-

ter purge system for proper operation.

Is the problem found?

Go toStep 5

Go toStep 6

5

Repair or replace any components as needed.
Is the repair complete?

System OK

6

1.  Disconnect all of the fuel injector harness con-

nectors.

2.  Connect an injector test light between the har-

ness terminals of each fuel injector.

3.  Note the test light while cranking the engine.

Does the test light blink on all connectors?

Go toStep 8

Go toStep 7

7

1.  Repair or replace the faulty fuel injector drive

harness, the connector, or the connector termi-
nal.

2.  If the connections and the harnesses are good,

replace the powertrain control module
PCM)/engine control module (ECM) for an in-
ternal open in the fuel injector driver circuit.

Is the repair complete?

System OK

8

Measure the resistance of each fuel injector. The re-
sistance will increase slightly at higher tempera-
tures.
Is the fuel injector resistance within the value speci-
fied?

11.6–12.4 

Ω

Go toStep 10

Go toStep 9

9

Replace any of the fuel injectors with a resistance
that is out of specifications.
Is the repair complete?

System OK

10

Perform an injector balance test.
Is the problem found?

Go toStep 11

Go toStep 12