Daewoo NUBIRA, Owner'S Manual

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1F – 404 I ENGINE CONTROLS
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 powertrain control module (PCM)/engine control mod-
ule (ECM). The PCM/ECM then determines Electronic
Spark Timing (EST) and triggers the direct 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 PCM/ECM to
control the electronic spark timing. The PCM/ECM uses
the following 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 powertrain control module (PCM)/engine control
module (ECM) to determine the crankshaft orientation at
all times. The PCM/ECM uses this information to generate
timed ignition and injection pulses that it sends to the igni-
tion coils and to the fuel injectors.
CAMSHAFT POSITION SENSOR
The Camshaft Position (CMP) sensor sends a CMP sen-
sor signal to the powertrain control module (PCM)/engine
control module (ECM). The PCM/ECM uses this signal as
a ”sync pulse” to trigger the injectors in the proper se-
quence. The PCM/ECM uses the CMP sensor signal to in-
dicate the position of the #1 piston during its power stroke.
This allows the PCM/ECM to calculate true sequential fuel
injection mode of operation. If the PCM/ECM detects an
incorrect 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 powertrain control module (PCM)/engine control
module (ECM) uses the IAC valve to set the idle speed de-
pendent on conditions. The PCM/ECM uses information
from various inputs, such as coolant temperature, man-
ifold 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 and the oxygen sensor O2S
1).
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
powertrain control module (PCM)/engine control module
(ECM) uses this information to richen the mixture, thus in-
creasing the fuel injector on–time, to provide the correct
amount of fuel. When decelerating, the vacuum in-
creases. This vacuum change is sensed by the MAP sen-
sor and read by the PCM/ECM, which then decreases the
fuel injector on–time due to the low fuel demand condi-
tions.
The O2S sensor is located in the exhaust manifold. The
O2S sensor indicates to the PCM/ECM the amount of oxy-
gen in the exhaust gas and the PCM/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 effi-