2004 DAEWOO LACETTI Throttle body

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DAEWOO V–121 BL4
7. Connect the fuel feed hose.
8. Connect the fuel injector harness connectors. Ro-
tate each fuel injector as required to avoid stretch-
ing the wireing harness.
9. Install the intake manifold bracket with the bolts.
10. Connect the negative battery cable.
11. Perform a leak check of the fuel rail and fuel injec-
tors.
FUEL RAIL AND INJECTORS
(1.8L DOHC)
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 system pressure. Refer to ” Fuel
System Pressure Relief ” in this section.
2. Disconnect the negative battery cable.
3. Disconnect the intake air temperature (IAT) sensor
connector.
4. Disconnect the breather hose from the valve cover.
5. Disconnect the positive crankcase ventilation (PCV)
hose from the valve cover.
6. Disconnect the throttle cables from the throttle body
and the bracket.
7. Disconnect the fuel feed line at the fuel rail.
8. Remove the fuel rail retaining bolts.

ENGINE CONTROLS 1F – 603
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Installation Procedure
1. Coat the threads of the ECT sensor with sealer.
2. Install the ECT sensor into the EI system ignition
coil adapter.
Tighten
Tighten the engine coolant temperature sensor to 20
NSm (15 lb–ft).
3. Connect the ECT sensor connector.
4. Fill the coolant system.
5. Connect the negative battery cable.
THROTTLE POSITION SENSOR
(1.8L DOHC)
Removal Procedure
1. Disconnect the negative battery cable.
2. Remove the air intake tube and resonator.
3. Disconnect the throttle position (TP) sensor con-
nector.
4. Remove the TP sensor retaining bolts and the TP
sensor.
Installation Procedure
1. With the throttle valve closed, position the TP sen-
sor on the throttle shaft. Align the TP sensor with
the bolt holes.
2. Install the TP sensor retaining bolts.
Tighten
Tighten the throttle position sensor retaining bolts to
2 NSm (18 lb–in).
3. Connect the TP sensor connector.
4. Install the air intake tube and resonator.
5. Connect the negative battery cable.
THROTTLE BODY (1.4L/1.6L DOHC)
Removal Procedure
1. Disconnect the negative battery cable.
2. Remove the intake air tube.
3. Disconnect the breather hose.

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4. Disconnect the coolant hose from the throttle body.
5. Disconnect the throttle cables by opening the re-
lease slot.
6. Disconnect the main throttle idle actuator (MTIA)
electrical connector.
7. Remove the throttle body bolt and the nuts.
8. Remove the throttle body.
Installation Procedure
1. Install the throttle body assembly to the intake man-
ifold.
2. Install the throttle body retaining nuts and the bolt.
Tighten
Tighten the throttle body retaining nuts and the bolt to
15 NSm (11 lb–ft).
3. Connect the throttle cable.
4. Connect the coolant hoses.
5. Connect the breather hose.
6. Install the intake air tube.
7. Connect the negative battery cable.
THROTTLE BODY (1.8L DOHC)
Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the intake air temperature (IAT) sensor
connector.
3. Disconnect the breather hose from the valve cover.
4. Remove the air intake tube.

ENGINE CONTROLS 1F – 605
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5. Disconnect the throttle cables by opening the
throttle and moving the cable through the release
slot.
6. Disconnect the vacuum hoses from the throttle
body.
7. Disconnect the throttle position (TP) sensor and the
idle air control valve connectors.
8. Disconnect the coolant hoses from the throttle
body.
9. Remove the throttle body retaining nuts.
Notice : Cover the opening of the intake manifold after re-
moving the throttle body assembly. This will prevent any
objects or debris from entering the engine which may
cause damage.
10. Remove the throttle body and discard the gasket.
11. Remove the TP sensor. Refer to ”Throttle Position
Sensor ”in this section.
12. Remove the idle air control (IAC) valve. Refer to
”Idle Air Control Valve ”in this section.
Installation Procedure
Notice : Use care in cleaning old gasket material from ma-
chined aluminum surfaces. Sharp tools may damage seal-
ing surfaces.
1. Clean the gasket mating surface on the intake man-
ifold.
Notice : The throttle body may be cleaned in a cold immer-
sion–type cleaner following disassembly. The TP sensor
and the idle air control valve should not come in contact
with any solvent or cleaner, as they may be damaged.
2. Clean the throttle body.
3. Install the TP sensor. Refer to ” Throttle Position
Sensor ”in this section.
4. Install the IAC valve. Refer to ”Idle Air Control Valve
” in this section.
5. Install the throttle body assembly with a new gasket
to the intake manifold.
6. Install the throttle body retaining nuts.
Tighten
Tighten the throttle body retaining nuts to 10 NSm (89
lb–in).

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7. Connect the TP sensor connector and the IAC
valve connector.
8. Connect the coolant hoses to the throttle body.
9. Connect the vacuum hoses to the throttle body.
Important : Make sure the throttle/cruise control cables
do not hold the throttle open. With the engine off, check to
see that the accelerator pedal is free.
10. Connect the throttle cable.
11. Install the air intake tube.
12. Connect the breather hose to the valve cover.
13. Connect the IAT sensor connector.
14. Connect the negative battery cable.
15. Fill the cooling system.
FRONT HEATED OXYGEN SENSOR
(HO2S1) (1.4L/1.6L DOHC)
Removal Procedure
1. Disconnect the negative battery cable.
Notice : The oxygen sensor uses a permanently attached
pigtail and connector. This pigtail should not be removed
from the oxygen sensor. Damage or removal of the pigtail
or the connector could affect proper operation of the oxy-
gen sensor. Take care when handling the oxygen sensor.
Do not drop the oxygen sensor.
2. Disconnect the front heated oxygen sensor
(HO2S1) connector.
Notice : The oxygen sensor may be difficult to remove
when engine temperature is below 48°C (120°F). Exces-
sive force may damage threads in the exhaust manifold.
3. Carefully remove the HO2S1 from the exhaust
manifold.
Installation Procedure
Important : A special anti–seize compound is used on the
oxygen sensor threads. This compound consists of a liq-
uid graphite and glass beads. The graphite will burn away,
but the glass beads will remain, making the sensor easier
to remove. New or service sensors will already have the
compound applied to the threads. If a sensor is removed
from any engine and if for any reason it is to be reinstalled,
the threads must have anti–seize compound applied be-
fore reinstallation.
1. Coat the threads of the HO2S1 with an anti–seize
compound, if needed.
2. Install the HO2S1 into the exhaust manifold.
Tighten
Tighten the oxygen sensor to 42 NSm (31 lb–ft).
3. Connect the HO2S1 connector.
4. Connect the negative battery cable.

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Notice : Do not use methyl ethyl ketone because it can
damage the parts.
6. Clean the IAC valve O–ring seal area, the pintle
valve seat, and the air passage with a suitable fuel
system cleaner.
Installation Procedure
Important : If installing a new IAC valve, be sure to re-
place it with an identical part. The IAC valve pintle shape
and diameter are designed for the specific application.
Measure the distance between the tip of the IAC valve
pintle and the mounting flange. If the distance is greater
than 1.1 inches (28 mm), use finger pressure to slowly re-
tract the pintle. The force required to retract the pintle will
not damage the IAC valve. The purpose of the 1.1–inch
(28–mm) setting is to prevent the IAC pintle from bottom-
ing out on the pintle seat. This 1.1–inch (28–mm) setting
is also an adequate setting for controlled idle on a restart.
1. Lubricate a new O–ring with engine oil. Install the
new O–ring onto the valve.
2. Install the IAC valve into the throttle body.
3. Install the IAC valve retaining bolts.
Tighten
Tighten the idle air control valve retaining bolts to 3
NSm (27 lb–in).
4. Connect the IAC valve connector.
5. Install the air intake resonator.
6. Connect the negative battery cable.
7. Start the engine and check for the proper idle
speed.
MANIFOLD ABSOLUTE PRESSURE
SENSOR (1.4L/1.6L DOHC)
Removal Procedure
1. Disconnect the negative battery cable.
2. Remove the manifold Absolute pressure (MAP)
sensor electrical connector.
3. Disconnect the MAP sensor vacuum hose.
4. Remove the MAP sensor bolt.
5. Remove the MAP sensor.

ENGINE CONTROLS 1F – 623
DAEWOO V–121 BL4
GENERAL DESCRIPTION
AND SYSTEM OPERATION
IGNITION SYSTEM OPERATION
This ignition system does not use a conventional distribu-
tor and coil. It uses a crankshaft position sensor input to
the engine control module (ECM). The ECM then deter-
mines Electronic Spark Timing (EST) and triggers the di-
rect ignition system ignition coil.
This type of distributorless ignition system uses a ”waste
spark” method of spark distribution. Each cylinder is
paired with the cylinder that is opposite it (1–4 or 2–3). The
spark occurs simultaneously in the cylinder coming up on
the compression stroke and in the cylinder coming up on
the exhaust stroke. The cylinder on the exhaust stroke re-
quires very little of the available energy to fire the spark
plug. The remaining energy is available to the spark plug
in the cylinder on the compression stroke.
These systems use the EST signal from the ECM to con-
trol the electronic spark timing. The ECM uses the follow-
ing information:
S Engine load (manifold pressure or vacuum).
S Atmospheric (barometric) pressure.
S Engine temperature.
S Intake air temperature.
S Crankshaft position.
S Engine speed (rpm).
ELECTRONIC IGNITION SYSTEM
IGNITION COIL
The Electronic Ignition (EI) system ignition coil provides
the spark for two spark plugs simultaneously. The EI sys-
tem ignition coil is not serviceable and must be replaced
as an assembly.
CRANKSHAFT POSITION SENSOR
This direct ignition system uses a magnetic crankshaft
position sensor. This sensor protrudes through its mount
to within approximately 0.05 inch (1.3 mm) of the crank-
shaft reluctor. The reluctor is a special wheel attached to
the crankshaft or crankshaft pulley with 58 slots machined
into it, 57 of which are equally spaced in 6 degree intervals.
The last slot is wider and serves to generate a ”sync
pulse.” As the crankshaft rotates, the slots in the reluctor
change the magnetic field of the sensor, creating an in-
duced voltage pulse. The longer pulse of the 58th slot
identifies a specific orientation of the crankshaft and al-
lows the engine control module (ECM) to determine the
crankshaft orientation at all times. The ECM uses this in-
formation to generate timed ignition and injection pulses
that it sends to the ignition coils and to the fuel injectors.
CAMAHAFT POSITION SENSOR
The Camshaft Position (CMP) sensor sends a CMP sen-
sor signal to the engine control module (ECM). The ECM
uses this signal as a ”sync pulse” to trigger the injectors in
the proper sequence. The ECM uses the CMP sensor sig-
nal to indicate the position of the #1 piston during its power
stroke. This allows the ECM to calculate true sequential
fuel injection mode of operation. If the ECM detects an in-
correct CMP sensor signal while the engine is running,
DTC P0341 will set. If the CMP sensor signal is lost while
the engine is running, the fuel injection system will shift to
a calculated sequential fuel injection mode based on the
last fuel injection pulse, and the engine will continue to run.
As long as the fault is present, the engine can be restarted.
It will run in the calculated sequential mode with a 1–in–6
chance of the injector sequence being correct.
IDLE AIR SYSTEM OPERATION
The idle air system operation is controlled by the base idle
setting of the throttle body and the Idle Air Control (IAC)
valve.
The engine control module (ECM) uses the IAC valve to
set the idle speed dependent on conditions. The ECM
uses information from various inputs, such as coolant tem-
perature, manifold vacuum, etc., for the effective control
of the idle speed.
FUEL CONTROL SYSTEM
OPERATION
The function of the fuel metering system is to deliver the
correct amount of fuel to the engine under all operating
conditions. The fuel is delivered to the engine by the indi-
vidual fuel injectors mounted into the intake manifold near
each cylinder.
The two main fuel control sensors are the Manifold Abso-
lute Pressure (MAP) sensor, the Front Heated Oxygen
Sensor (HO2S1) and the Rear Heated Oxygen Sensor
(HO2S2).
The MAP sensor measures or senses the intake manifold
vacuum. Under high fuel demands the MAP sensor reads
a low vacuum condition, such as wide open throttle. The
engine control module (ECM) uses this information to ri-
chen the mixture, thus increasing the fuel injector on–time,
to provide the correct amount of fuel. When decelerating,
the vacuum increases. This vacuum change is sensed by
the MAP sensor and read by the ECM, which then de-
creases the fuel injector on–time due to the low fuel de-
mand conditions.
HO2S Sensors
The HO2S sensor is located in the exhaust manifold. The
HO2S sensor indicates to the ECM the amount of oxygen
in the exhaust gas and the ECM changes the air/fuel ratio
to the engine by controlling the fuel injectors. The best air/
fuel ratio to minimize exhaust emissions is 14.7 to 1, which
allows the catalytic converter to operate most efficiently.

ENGINE CONTROLS 1F – 625
DAEWOO V–121 BL4
EVAPORATIVE EMISSION CANISTER
The Evaporative (EVAP) Emission canister is an emission
control device containing activated charcoal granules.
The EVAP emission canister is used to store fuel vapors
from the fuel tank. Once certain conditions are met, the en-
gine control module (ECM) activates the EVAP canister
purge solenoid, allowing the fuel vapors to be drawn into
the engine cylinders and burned.
POSITIVE CRANKCASE
VENTILATION SYSTEM OPERATION
A Positive Crankcase Ventilation (PCV) system is used to
provide complete use of the crankcase vapors. Fresh air
from the air cleaner is supplied to the crankcase. The fresh
air is mixed with blowby gases which are then passed
through a vacuum hose into the intake manifold.
Periodically inspect the hoses and the clamps. Replace
any crankcase ventilation components as required.
A restricted or plugged PCV hose may cause the following
conditions:
S Rough idle
S Stalling or low idle speed
S Oil leaks
S Oil in the air cleaner
S Sludge in the engine
A leaking PCV hose may cause the following conditions:
S Rough idle
S Stalling
S High idle speed
ENGINE COOLANT TEMPERATURE
SENSOR
The Engine Coolant Temperature (ECT) sensor is a
thermistor (a resistor which changes value based on tem-
perature) mounted in the engine coolant stream. Low cool-
ant temperature produces a high resistance (100,000
ohms at –40 °F [–40 °C]) while high temperature causes
low resistance (70 ohms at 266 °F [130 °C]).
The engine control module (ECM) supplies 5 volts to the
ECT sensor through a resistor in the ECM and measures
the change in voltage. The voltage will be high when the
engine is cold, and low when the engine is hot. By measur-
ing the change in voltage, the ECM can determine the
coolant temperature. The engine coolant temperature af-
fects most of the systems that the ECM controls. A failure
in the ECT sensor circuit should set a diagnostic trouble
code P0117 or P0118. Remember, these diagnostic
trouble codes indicate a failure in the ECT sensor circuit,
so proper use of the chart will lead either to repairing a wir-
ing problem or to replacing the sensor to repair a problem
properly.
THROTTLE POSITION SENSOR
The Throttle Position (TP) sensor is a potentiometer con-
nected to the throttle shaft of the throttle body. The TP sen-
sor electrical circuit consists of a 5 volt supply line and a
ground line, both provided by the engine control module
(ECM). The ECM calculates the throttle position by moni-
toring the voltage on this signal line. The TP sensor output
changes as the accelerator pedal is moved, changing the
throttle valve angle. At a closed throttle position, the output
of the TP sensor is low, about 0.5 volt. As the throttle valve
opens, the output increases so that, at Wide Open Throttle
(WOT), the output voltage will be about 5 volts.
The ECM can determine fuel delivery based on throttle
valve angle (driver demand). A broken or loose TP sensor
can cause intermittent bursts of fuel from the injector and
an unstable idle, because the ECM thinks the throttle is
moving. A problem in any of the TP sensor circuits should
set a diagnostic trouble code (DTC) P0121 or P0122.
Once the DTC is set, the ECM will substitute a default val-
ue for the TP sensor and some vehicle performance will
return. A DTC P0121 will cause a high idle speed.
CATALYST MONITOR OXYGEN
SENSORS
Three–way catalytic converters are used to control emis-
sions of hydrocarbons (HC), carbon monoxide (CO), and
oxides of nitrogen (NOx). The catalyst within the convert-
ers promotes a chemical reaction. This reaction oxidizes
the HC and CO present in the exhaust gas and converts
them into harmless water vapor and carbon dioxide. The
catalyst also reduces NOx by converting it to nitrogen. The
engine control module (ECM) can monitor this process us-
ing the HO2S1 and HO2S2 sensor. These sensors pro-
duce an output signal which indicates the amount of oxy-
gen present in the exhaust gas entering and leaving the
three–way converter. This indicates the catalyst’s ability to
efficiently convert exhaust gasses. If the catalyst is operat-
ing efficiently, the HO2S1 sensor signals will be more ac-
tive than the signals produced by the HO2S2 sensor. The
catalyst monitor sensors operate the same way as the fuel
control sensors. The sensor’s main function is catalyst
monitoring, but they also have a limited role in fuel control.
If a sensor output indicates a voltage either above or below
the 450 mv bias voltage for an extended period of time, the
ECM will make a slight adjustment to fuel trim to ensure
that fuel delivery is correct for catalyst monitoring.
A problem with the HO2S1 sensor circuit will set DTC
P0131, P0132, P0133 or P0134 depending, on the special
condition. A problem with the HO2S2 sensor signal will set
DTC P0137, P0138, P0140 or P0141, depending on the
special condition.
A fault in the Rear Heated Oxygen Sensor (HO2S2) heat-
er element or its ignition feed or ground will result in lower
oxygen sensor response. This may cause incorrect cata-
lyst monitor diagnostic results.