2004 DAEWOO NUBIRA engine e

1F – 588IENGINE CONTROLS
DAEWOO V–121 BL4
ROUGH, UNSTABLE, OR INCORRECT LDLE, STALLING
Definition : The engine runs unevenly at idle. If the condi-
tion is bad enough, the vehicle may shake. Also, the idle
varies in rpm (called ”hunting”). Either condition may be
severe enough to cause stalling. The engine idles at incor-
rect idle speed.Important : Before diagnosing the symptom, check ser-
vice bulletins for updates.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Connect the scan tool to the Data Link Con-
nector (DLC).
2. Monitor the Front Heated Oxygen Sensor
(HO2S1) reading at different throttle positions.
Does the HO2S sensor change quickly from rich to
lean at the different throttle positions?–Go toStep 5Go toStep 3
3Check the HO2S1 sensor for contamination from
fuel or improper use of Room Temperature Vulcaniz-
ing (RTV) sealant.
Is the HO2S1 sensor contaminated?–Go toStep 4Go toStep 5
4Replace the contaminated HO2S sensor as needed.
Is the repair complete?–System OK–
51. Check for a sticking throttle shaft or binding
throttle linkage that may cause incorrect
Throttle Position (TP) sensor voltage.
2. Check the TP sensor voltage reading with the
throttle closed.
Is the TP sensor voltage within the value specified?0.4–0.8 vGo toStep 6Go to
”Diagnostic
Aids for DTC
P0123”
61. Check the Engine Coolant Temperature (ECT)
sensor voltage reading using the scan tool.
2. Compare the ECT reading with the ambient
temperature when the engine is cold.
Does the ECT temperature reading differ from the
ambient temperature by more than the value speci-
fied?5°F (3°C)Go toStep 7Go toStep 9
7Check for high resistance in the ECT sensor circuit
or the sensor itself.
Is the problem found?–Go toStep 8Go toStep 9
8Replace the ECT sensor or repair the circuit as
needed.
Is the repair complete?–System OK–
9Check the Manifold Absolute Pressure (MAP) sen-
sor for response and accuracy.
Is the problem found?–Go toStep 10Go toStep 11
10Replace the MAP sensor or repair the MAP sensor
circuit as needed.
Is the repair complete?–System OK–

ENGINE CONTROLS 1F – 589
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
111. Road test the vehicle at the speed of the com-
plaint.
2. Monitor the fuel trim reading using the scan
tool.
Is the fuel trim reading within the value specified?–20–25%Go toStep 14Go toStep 12
12Is the fuel trim reading below the value specified?–20%Go to
”Diagnostic
Aids for DTC
P0172”Go toStep 13
13Is the fuel trim reading above the value specified?25%Go to
”Diagnostic
Aids for DTC
P0171”–
141. Disconnect all of the fuel injector harness con-
nectors at the fuel injectors.
2. Connect an injector test light between the har-
ness terminals of each fuel injector connector.
3. Note the test light while cranking the engine.
Does the test light blink for all of the fuel injectors?–Go toStep 16Go toStep 15
151. Repair or replace the faulty injector drive circuit
harness, the connector, or the connector termi-
nals as needed.
2. If the harness, the connectors, and the termi-
nals are OK, replace the engine control module
(ECM).
Is the repair complete?–System OK–
16Measure the resistance of each of the fuel injectors.
The resistance will increase slightly at higher tem-
peratures.
Is the resistance within the value specified?11.6–12.4 ΩGo toStep 18Go toStep 17
17Replace any fuel injectors with a resistance that is
out of specifications.
Is the repair complete?–System OK–
18Perform an injector balance test.
Is the problem found?–Go toStep 19Go toStep 20
19Replace any leaking or restricted fuel injectors.
Is the repair complete?–System OK–
201. With the engine OFF, disconnect the fuel pres-
sure regulator vacuum hose.
2. Thoroughly inspect the fuel pressure regulator
vacuum port and the fuel pressure regulator
vacuum hose for the presence of fuel.
Is the problem found?–Go toStep 21 Go toStep 22
21Replace the fuel pressure regulator as needed.
Is the repair complete?–System OK–

1F – 590IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
221. Check the ignition system output voltage for all
of the cylinders using a spark tester.
2. Inspect the spark plugs for excessive wear,
insulation cracks, improper gap, or heavy de-
posits.
3. Inspect the ignitionwires for cracking, hard-
ness, or improper connections.
4. Replace any ignition wires with a resistance
over the value specified.
Is the problem found?3,000 ΩGo toStep 23Go toStep 24
23Repair or replace any ignition system components
as needed.
Is the repair complete?–System OK–
241. Inspect for vacuum leaks.
2. Check for proper Positive Crankcase Ventila-
tion (PCV) operation.
3. Check the Idle Air Control (IAC) valve opera-
tion.
4. Inspect the ECM ground connections.
Is the problem found?–Go toStep 25Go toStep 26
25Repair or replace any components as needed.
Is the repair complete?–System OK–
261. Check the Exhaust Gas Recirculation (EGR)
valve for proper operation.
2. Inspect the battery cables and the ground
straps for proper connections.
3. Check the generator voltage output. Repair or
replace the generator if the voltage output is
not within the value specified.
Is the problem found?12–16 vGo toStep 27Go toStep 28
27Repair or replace any components as needed.
Is the repair complete?–System OK–
281. Inspect for broken engine mounts.
2. Check for proper valve timing.
3. Perform a cylinder compression test.
4. Inspect for bent pushrods, worn rocker arms,
broken or weak valve springs, and a worn cam-
shaft.
5. Perform repairs as needed.
Are all of the checks and needed repairs complete?–System OK–

ENGINE CONTROLS 1F – 591
DAEWOO V–121 BL4
EXCESSIVE EXHAUST EMISSIONS OR ODORS
Definition : A vehicle fails an emission test. The vehicle
has an excessive rotten egg smell.Important : Excessive odors do not necessarily indicate
excessive emissions.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Run the engine until it reaches operating tem-
perature.
2. Perform an emission test.
Does the vehicle pass the emission test?–System OKGo toStep 3
31. Connect the scan tool to the Data Link Con-
nector (DLC).
2. Road test the vehicle.
3. Monitor the long term fuel trim memory.
Is the long term fuel trim memory within the value
specified?–20–25%Go toStep 6Go toStep 4
4Is the long term fuel trim memory below the value
specified?–20%Go to
”Diagnostic
Aids for DTC
P0172”Go toStep 5
5Is the long term fuel trim memory above the value
specified?25%Go to
”Diagnostic
Aids for DTC
P0171”–
61. Check for a properly installed fuel cap.
2. Check the fuel system pressure.
3. Perform an injector balance test.
Is the problem found?–Go toStep 7Go toStep 8
71. Repair or replace any fuel system components
as needed.
2. Perform an emission test.
Does the vehicle pass the emission test?–System OK–
81. Check the ignition system for proper operation.
2. Inspect the spark plugs for excessive wear,
insulation cracks, improper gap, or heavy de-
posits.
3. Check the ignition wires for cracking, hardness,
or improper connections.
Is the problem found?–Go toStep 9Go toStep 10

1F – 592IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
91. Repair or replace any ignition system compo-
nents as needed.
2. Perform an emission test.
Does the vehicle pass the emission test?–System OK–
101. Inspect for vacuum leaks.
2. Inspect the catalytic converter for contamina-
tion.
3. Inspect for carbon buildup on the throttle body
and the throttle plate and inside the engine.
Remove with a top engine cleaner.
4. Check the Exhaust Gas Recirculation (EGR)
valve to make sure it opens.
5. Check for proper Positive Crankcase Ventila-
tion (PCV) operation.
Are all checks and needed repairs complete?–System OK–
DIESELING, RUN–ON
Definition : An engine continues to run after the ignition switch is turned OFF.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
2Does the engine run smoothly after the ignition
switch is turned OFF?–Go toStep 3Go toStep 4
31. Check the ignition switch and the ignition
switch adjustment.
2. Replace the ignition switch if needed.
Is the repair complete?–System OK–
41. Check the evaporative emission system.
2. Check for leaking fuel injectors.
3. Check the Idle Air Control (IAC) valve opera-
tion.
4. Inspect for vacuum leaks.
5. Check for the proper base idle setting.
Are all checks and repairs complete?–System OK–

ENGINE CONTROLS 1F – 593
DAEWOO V–121 BL4
BACKFIRE
Definition : Fuel ignites in the intake manifold, or in the ex-
haust system, making a loud popping noise.Important : Before diagnosing the symptom, check ser-
vice bulletins for updates.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Inspect for crossed or crossfiring ignition wires.
2. Check the ignition system output voltage for all
cylinders using a spark tester.
3. Inspect the spark plugs for excessive wear,
burned electrodes, improper gap, or heavy de-
posits..
Is the problem found?–Go toStep 3Go toStep 4
3Repair or replace any ignition system components
as needed.
Is the repair complete?–System OK–
41. Check the fuel system operation.
2. Check the fuel injectors by performing an injec-
tor diagnosis.
Is the problem found?–Go toStep 5Go toStep 6
5Repair or replace any fuel system components as
needed.
Is the repair complete?–System OK–
61. Inspect the Exhaust Gas Recirculation (EGR)
gasket for a leak or a loose fit.
2. Check the EGR valve for proper operation.
3. Inspect the intake manifold and the exhaust
manifold for a casting flash.
Is the problem found?–Go toStep 7Go toStep 8
7Repair or replace any components as needed.
Is the repair complete?–System OK–
81. Inspect the timing belt for proper installation
and tension.
2. Check the engine compression.
3. Inspect the intake manifold gasket and the ex-
haust manifold gasket for leaks.
4. Check for sticking or leaking valves.
5. Repair or replace any components as needed.
Are all checks and corrections complete?–System OK–

1F – 594IENGINE CONTROLS
DAEWOO V–121 BL4
MAINTENANCE AND REPAIR
ON–VEHICLE SERVICE
FUEL SYSTEM PRESSURE RELIEF
Procedure
CAUTION : The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
fire, it is necessary to relieve the fuel system pressure
before disconnecting the fuel lines.
1. Remove the fuel cap.
2. Remove the fuel pump fuse Ef18 from the engine
fuse block.
3. Start the engine and allow the engine to stall.
4. Crank the engine for an additional 10 seconds.
FUEL TANK
Removal Procedure
CAUTION : The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
fire, it is necessary to relieve the fuel system pressure
before disconnecting the fuel lines.
1. Relieve the fuel pressure. Refer to ” Fuel System
Pressure Relief ” in this section.
2. Disconnect the negative battery cable.
3. Drain the fuel tank.
4. Remove the front muffler. Refer to Section 1G, Ex-
haust System
5. Remove the fuel tank filler tube clamp at the fuel
tank.
6. Disconnect the fuel tank filler tube.
7. Disconnect the fuel vapor line near the fuel tank
filler tube.
8. Disconnect the fuel pump harness connector.

ENGINE CONTROLS 1F – 595
DAEWOO V–121 BL4
9. Disconnect the fuel inlet line and the fuel return line
near the right front of the fuel tank.
10. Remove the Fuel pump. Refer to ”Fuel Pump” in
this section.
11. Remove the parking brake cables support brackets.
12. Support the fuel tank.
13. Remove the fuel tank strap retaining nuts.
14. Remove the fuel tank strap.
15. Carefully lower the fuel tank.
16. Remove the fuel tank.
17. Transfer any parts as needed.
Installation Procedure
1. Raise the fuel tank into position.
2. Install the fuel tank straps.
3. Install the fuel tank strap retaining nuts.
Tighten
Tighten the fuel tank strap retaining nuts to 20 NSm
(15 lb–ft).
4. Install the parking brake cables support bracket.
5. Install the fuel pump. Refer to ”Fuel Pump” in this
section.
6. Connect the fuel outlet line and the fuel return line.