Daewoo Nubira. Manual — part 122
1F – 372
I
ENGINE CONTROLS
DAEWOO V–121 BL4
Step
No
Yes
Value(s)
Action
11
1. 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?
115–150
counts
Go toStep 14
Go toStep 12
12
Is the fuel trim reading below the value specified?
115 counts
Go to”Diagnos-
tic Aids for
DTC P0172”
Go toStep 13
13
Is the fuel trim reading above the value specified?
150 counts
Go to”Diagnos-
tic Aids for
DTC P0171”
14
1. 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 16
Go toStep 15
15
1. 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 powertrain control
module (PCM)/engine control module (ECM).
Is the repair complete?
System OK
16
Measure 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
Ω
Go toStep 18
Go toStep 17
17
Replace any fuel injectors with a resistance that is
out of specifications.
Is the repair complete?
System OK
18
Perform an injector balance test.
Is the problem found?
Go toStep 19
Go toStep 20
19
Replace any leaking or restricted fuel injectors.
Is the repair complete?
System OK
20
1. 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
21
Replace the fuel pressure regulator as needed.
Is the repair complete?
System OK
ENGINE CONTROLS 1F – 373
DAEWOO V–121 BL4
Step
No
Yes
Value(s)
Action
22
1. 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?
30,000
Ω
Go toStep 23
Go toStep 24
23
Repair or replace any ignition system components
as needed.
Is the repair complete?
System OK
24
1. 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 PCM/ECM ground connections.
Is the problem found?
Go toStep 25
Go toStep 26
25
Repair or replace any components as needed.
Is the repair complete?
System OK
26
1. 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 v
Go toStep 27
Go toStep 28
27
Repair or replace any components as needed.
Is the repair complete?
System OK
29
1. 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
1F – 374
I
ENGINE CONTROLS
DAEWOO V–121 BL4
EXCESSIVE EXHAUST EMISSIONS OR ODORS
A vehicle fails an emission test. The vehicle has an excessive rotten egg smell.
Important : Excessive odors do not necessarily indicate excessive emissions.
Step
Action
Value(s)
Yes
No
1
Were the Important Preliminary Checks performed?
Go toStep 2
Go to”Impor-
tant Preliminary
Checks”
2
1. Run the engine until it reaches operating tem-
perature.
2. Perform an emission test.
Does the vehicle pass the emission test?
System OK
Go toStep 3
3
1. 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?
115–150
counts
Go toStep 6
Go toStep 4
4
Is the long term fuel trim memory below the value
specified?
115 counts
Go to”Diagnos-
tic Aids for
DTC P0172”
Go toStep 5
5
Is the long term fuel trim memory above the value
specified?
150 counts
Go to”Diagnos-
tic Aids for
DTC P0171”
6
1. 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 7
Go toStep 8
7
1. Repair or replace any fuel system components
as needed.
2. Perform an emission test.
Does the vehicle pass the emission test?
System OK
8
1. 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 9
Go toStep 10
ENGINE CONTROLS 1F – 375
DAEWOO V–121 BL4
Step
No
Yes
Value(s)
Action
9
1. Repair or replace any ignition system compo-
nents as needed.
2. Perform an emission test.
Does the vehicle pass the emission test?
System OK
10
1. 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
An engine continues to run after the ignition switch
is turned OFF.
Step
Action
Value(s)
Yes
No
1
Were the Important Preliminary Checks performed?
Go toStep 2
Go to”Impor-
tant Preliminary
Checks”
2
Does the engine run smoothly after the ignition
switch is turned OFF?
Go toStep 3
Go toStep 4
3
1. Check the ignition switch and the ignition
switch adjustment.
2. Replace the ignition switch if needed.
Is the repair complete?
System OK
4
1. 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
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