engine controls DAEWOO LACETTI 2004 Service Repair Manual

ENGINE CONTROLS 1F – 581
DAEWOO V–121 BL4
LACK OF POWER, SLUGGISHNESS, OR SPONGINESS
Definition : The engine delivers less than expected power. There is little or no increase in speed when the accelerator pedal
is partially applied.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Verify the customer’s complaint.
2. Compare the performance of the customer’s
vehicle with a similar unit.
Does the problem exist?–Go toStep 3System OK
31. 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 4Go toStep 5
4Check the fuel system pressure.
Is the fuel system pressure within specifications?41–47 psi
(284–325 kPa)Go toStep 7Go toStep 6
5Repair the transaxle as needed.
Is the repair complete?–System OK–
6Repair the fuel system as needed.
Is the repair complete?–System OK–
7Check for a restricted fuel filter or contaminated fuel.
Is the problem found?–Go toStep 8Go toStep 9
8Repair or replace any components as needed.
Is the repair complete?–System OK–
91. 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 10Go toStep 11
101. 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 12Go toStep 15
11Repair or replace any ignition system components
as needed.
Is the repair complete?–System OK–
12Inspect the exhaust system for restrictions and dam-
aged or collapsed pipes.
Is the problem found?–Go toStep 13Go toStep 15
13Repair or replace any components as needed.
Is the repair complete?–System OK–

1F – 582IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
141. Check the cylinder compression and valve tim-
ing.
2. Inspect the camshaft for excessive wear.
Is the problem found?–Go toStep 15Go toStep 16
15Repair or replace any engine components as need-
ed.
Is the repair complete?–System OK–
161. Check the engine control module (ECM)
grounds for being clean, tight, and in their prop-
er location.
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 vSystem OK–

ENGINE CONTROLS 1F – 583
DAEWOO V–121 BL4
HESITATION, SAG, STUMBLE
Definition : 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
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. 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 3Go toStep 4
3Repair or replace any components as needed.
Is the repair complete?–System OK–
41. 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 5Go toStep 6
5Repair or replace any components as needed.
Is the repair complete?–System OK–
61. 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 8Go toStep 7
71. 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 engine control module (ECM) for
an internal open in the fuel injector driver cir-
cuit.
Is the repair complete?–System OK–
8Measure 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 ΩGo toStep 10Go toStep 9
9Replace any of the fuel injectors with a resistance
that is out of specifications.
Is the repair complete?–System OK–
10Perform an injector balance test.
Is the problem found?–Go toStep 11Go toStep 12

1F – 584IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
11Replace any restricted or leaking fuel injectors.
Is the repair complete?–System OK–
12Check the fuel system pressure after a cold start or
during moderate or full throttle acceleration.
Is the fuel pressure within specifications?41–47 psi
(284–325 kPa)Go toStep 14Go toStep 13
13Repair the restriction in the fuel system or replace
the faulty fuel pump.
Is the repair complete?–System OK–
141. Check for faulty ignition wires.
2. Inspect for fouled spark plugs.
3. Check the ignition system output on each cylin-
der with a spark tester.
Is the problem found?–Go toStep 15Go toStep 16
15Repair or replace any ignition components as need-
ed.
Is the repair complete?–System OK–
161. Check the generator output voltage.
2. Repair or replace the generator if the generator
output is less than the value specified.
3. Check the Exhaust Gas Recirculation (EGR)
valve operation.
Are all checks and needed repairs complete?12–16 vSystem OK–
CUTS OUT, MISSES
Definition : This Involves a steady pulsation or jerking that follows engine speed, usually more pronounced as engine load
increases. The exhaust has a steady spitting sound at idle or low speed.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
2Check the ignition system output voltage for all of the
cylinders using a spark tester.
Is spark present on all of the cylinders?–Go toStep 3Go to
”Ignition Sys-
tem Check”
31. Inspect the spark plugs for excessive wear,
insulation cracks, improper gap, or heavy de-
posits.
2. Check the resistance of the ignition wires. Re-
place any ignition wires that have a resistance
greater than the value specified.
Is the problem found?3,000 ΩGo toStep 4Go toStep 5
4Repair or replace any components as needed.
Is the repair complete?–System OK–
5With the engine running, spray the ignition wires with
a fine water mist to check for arcing and shorting to
ground.
Is the problem found?–Go toStep 6Go toStep 7
6Replace the ignition wires.
Is the repair complete?–System OK–

ENGINE CONTROLS 1F – 585
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
71. Perform a cylinder compression test.
2. If the compression is low, repair the engine as
needed.
3. Inspect for proper valve timing, bent pushrods,
worn rocker arms, broken or weak valve
springs, and worn camshaft lobes.
4. Inspect the intake manifold and the exhaust
manifold passages for casting flash.
Is the problem found?–Go toStep 8Go toStep 9
8Repair or replace any components as needed.
Is the repair complete?–System OK–
91. Check the fuel system for a plugged in–line fuel
filter.
2. Check the fuel system for low fuel pressure. If
the fuel pressure is below the value specified,
service the fuel system as needed.
3. Inspect for contaminated fuel.
Is the problem found?41–47 psi
(284–325 kPa)Go toStep 10Go toStep 11
10Repair or replace any components as needed.
Is the repair complete?–System OK–
111. Disconnect all of the fuel injector harness con-
nectors at the fuel injectors.
2. Connect an injector test light to the harness
terminals of each fuel injector connector.
3. Note the test light while cranking the engine for
each fuel injector.
Does the test light blink for all of the fuel injectors?–Go toStep 13Go toStep 12
121. Repair or replace the faulty injector drive circuit
harness, the connector, or the connector termi-
nal.
2. If the harness, the connectors, and the termi-
nals are OK, replace the engine control module
(ECM).
Is the repair complete?–System OK–
13Measure the resistance of each fuel injector. The re-
sistance will increase slightly at higher tempera-
tures.
Is the injector resistance within the value specified?11.6–12.4 ΩGo toStep 15Go toStep 14
14Replace any fuel injectors with a resistance that is
out of specifications.
Is the repair complete?–System OK–
15Perform an injector balance test.
Is the problem found?–Go toStep 16Go toStep 17
16Replace any restricted or leaking fuel injectors.
Is the repair complete?–System OK–

1F – 586IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
171. Check for electromagnetic interference.
2. Monitor the engine rpm with a scan tool.
Does the scan tool rpm change greatly with little
change in actual engine rpm?–Go toStep 18–
181. Inspect the routing of the ignition wires.
2. Inspect all of the ignition system grounds.
3. Correct the routing or repair the ground con-
nections as needed.
Are all checks and needed repairs complete?–System OK–

ENGINE CONTROLS 1F – 587
DAEWOO V–121 BL4
POOR FUEL ECONOMY
Definition : Fuel economy, as measured by an actual road
test, is noticeably lower than expected. Also, fuel econo-
my is noticeably lower than it was on this vehicle at one
time, as previously shown by an actual road test.
Important : Driving habits affect fuel economy. Check the
owner’s driving habits by asking the following questions:1. Is the A/C system (i.e. defroster mode) turned on
all the time?
2. Are the tires at the correct air pressure?
3. Have excessively heavy loads been carried?
4. Does the driver accelerate too much and too often?
Suggest the driver read the section in the owner’s
manual about fuel economy.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Inspect the air filter for excessive contamina-
tion.
2. Inspect for fuel system leaks.
Are all needed checks complete?–Go toStep 3–
31. Inspect the spark plugs for excessive wear,
insulation cracks, improper gap, or heavy de-
posits.
2. Replace any faulty spark plugs.
3. Inspect the ignition wires for cracking, hard-
ness, and proper connections.
Are all needed checks and repairs complete?–Go toStep 4–
41. Inspect the engine coolant level.
2. Check the thermostat for being always open or
for an incorrect heat range.
3. Replace the thermostat as needed.
Are all needed checks and repairs complete?–Go toStep 5–
51. Check the transaxle shift pattern. Ensure all
transaxle gears are functioning.
2. Check the Torque Converter Clutch (TCC) op-
eration with a scan tool. The scan tool should
indicate rpm drop when the TCC is command-
ed on.
3. Check for proper calibration of the speedome-
ter.
4. Check the brakes for dragging.
5. Check the cylinder compression.
6. Repair, replace, or adjust any components as
needed.
Are all checks and needed repairs complete?–System OK–

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–