2004 DAEWOO LACETTI compression ratio

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 – 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–

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.