fuel CHEVROLET DYNASTY 1993 Service Manual

POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEMS
Intake manifold vacuum removes crankcase vapors
and piston blow-by from the engine. The emissions pass
through the PCV valve into the intake manifold where
they become part of the calibrated air-fuel mixture.
They are burned and expelled with the exhaust gases.
The air cleaner supplies make up air when the engine
does not have enough vapor or blow-by gases. In this
system, fresh air does not enter the crankcase (Figs. 10,
11, 12, 13, 14, 15, and 16).
PCV VALVE TEST
WARNING: APPLY PARKING BRAKE AND/OR
BLOCK WHEELS BEFORE PERFORMING ANY TEST
OR ADJUSTMENT WITH THE ENGINE OPERATING. With the engine idling, remove the PCV valve
from its attaching point. If the valve is operating
properly, a hissing noise will be heard and a strong
vacuum felt when placing a finger over the valve in-
let (Fig. 17). With the engine off, the shake the
valve. The valve should rattle when shaken. Replace
the valve if it does not operate properly. Do not at-
tempt to clean the PCV valve.
Fig. 10 PCV ValveÐ2.5L TBI Engine
Fig. 11 PCV SystemÐ2.5L MPI (Flexible Fuel)
Fig. 12 PCV SystemÐTurbo III Engine
Fig. 13 PCV SystemÐ3.0L Engine
Ä EMISSION CONTROL SYSTEMS 25 - 15

CRANKCASE VENT FILTER
All engines have a crankcase vent filter. The filter
cleans outside air before it enters the PCV system.
On 2.5L engines, the filter mounts to the upper shell
assembly of the air cleaner. On 2.5L MPI (Flexible
Fuel AA-body) and Turbo III engines, the filter at-
taches to the inside of the filter element box, next to
the filter element. On 3.0L engines, it attaches to the
inside of the filter element box under the filter ele- ment. On the 3.3L engines, the filter mounts to the
bottom of the filter element box. Refer to Group 0 for
mileage intervals and service procedures.
Fig. 14 PCV ValveÐ3.0L Engine
Fig. 15 PCV System Fresh Air HoseÐ3.0L Engine
Fig. 16 PCV SystemÐ3.3L/3.8L Engines
Fig. 17 Typical PCV Test
25 - 16 EMISSION CONTROL SYSTEMS Ä

EXHAUST EMISSION CONTROLS INDEX
page page
Air Aspiration System ..................... 24
EGR Gas Flow Test ...................... 21
EGR System On-Board Diagnostics ........... 21
EGR Tube ServiceÐ2.2L and 2.5L TBI Engines . 22
EGR Tube ServiceÐ3.0L Engines ............ 22
EGR Tube ServiceÐ3.3L and 3.8L Engines .... 22
EGR Valve ServiceÐ2.2L and 2.5L TBI Engines . 22 EGR Valve ServiceÐ3.0L Engines
........... 22
EGR Valve ServiceÐ3.3L and 3.8L Engines .... 22
Exhaust Gas Recirculation (EGR) System ...... 20
Exhaust Gas Recirculation (EGR) System Test . . 21
Heated Inlet Air System ................... 17
Heated Oxygen Sensor (O
2Sensor) .......... 18
HEATED INLET AIR SYSTEM
2.5L MPI (Flexible Fuel AA-body), Turbo III, 3.0L,
3.3L and 3.8L engines do not use a heated inlet air
system. 2.2L and 2.5L TBI air cleaners have a heated air
assembly (Fig. 1). When ambient temperatures are
low, the assembly warms the air before it enters the
throttle body. The heated air assembly reduces hy-
drocarbon emissions, improves engine warm-up char-
acteristics and minimizes icing.
The heated air assembly contains a vacuum oper-
ated blend door. The blend door opens to either
heated air from a stove on the exhaust manifold or
ambient air (outside air). A vacuum diaphragm oper-
ates the door. A spring opposes the vacuum dia-
phragm. A temperature sensor controls the vacuum
diaphragm (Fig. 2). Adjustment of inlet air tempera-
ture occurs only at road load throttle positions or
when the intake manifold vacuum exceeds the vac-
uum diaphragm spring rate. Air flows through the outside air inlet when ambi-
ent air temperature is 8ÉC (15ÉF) or more above the
air temperature sensor control temperature. When ambient air temperature falls below the con-
trol temperature, air flows through both the ambient
and heated circuits. This occurs after the engine has
been started and the exhaust manifold starts to give
off heat. Colder ambient air cause greater air flow
through the heat stove on the exhaust manifold.
Warmer ambient air results in greater ambient air
flow through the air cleaner snorkel.
HEATED INLET AIR SYSTEM SERVICE
Heated air inlet system malfunctions may affect
driveability and vehicle exhaust emissions. Use the following procedure to determine if the
system functions properly. (1) Inspect the condition of the heat stove to air
cleaner flexible connector and all vacuum hoses. In-
spect them for proper attachment. Replace as neces-
sary. (2) With a cold engine and ambient temperature
less than 46ÉC (115ÉF.), the heat control door (valve
plate) should be in the up (heat on position).
(3) With the engine warmed up and running,
check the temperature of the air entering the snorkel
or passing the sensor. When the temperature of the
Fig. 1 Heated Air Inlet System
Fig. 2 Heated Air Temperature Sensor
Ä EMISSION CONTROL SYSTEMS 25 - 17

air entering the outer end of snorkel is 60ÉC (140ÉF.) or
higher, the door should be in the down (heat off)
position. (4) Remove the air cleaner from the engine and
allow it to cool down to 46ÉC (115ÉF). With 20 inches of
vacuum applied to the sensor, the door should be in the
up (heat on position). If the door does not rise to the
heat on position, check the vacuum diaphragm for
proper operation. (5) To test the diaphragm, apply 20 inches of vacuum
to it with vacuum pump tool number C-4207 or equiva-
lent (Fig. 3). The diaphragm should not bleed down
more than 10 inches of vacuum in 5 minutes. The door
should not lift off the bottom of the snorkel at less than
2 inches of vacuum. The door should be in the full up
position with no more than 4 inches of vacuum. (6) If the vacuum diaphragm does not perform ad-
equately, replace the heated air assembly.
(7) If the vacuum diaphragm performs adequately
but proper temperature is not maintained, replace the
sensor and repeat the temperature checks in steps 2
and 3.
HEATED AIR TEMPERATURE SENSOR SER- VICE
REMOVAL
(1) Remove air cleaner housing from vehicle.
(2) Disconnect vacuum hoses from air temperature
sensor. Remove and discard retainer clips, new clips
are supplied with a new sensor (Fig. 4). (3) Remove and discard sensor and gasket.
INSTALLATION (1) Position gasket on the sensor. Install sensor (Fig.
5). (2) While supporting the sensor on outer diameter,
install new retainer clips securely. Ensure the gasket
compresses to form an air seal. Do not attempt to
adjust the sensor.
HEATED OXYGEN SENSOR (O2SENSOR)
The O2sensor threads into the exhaust manifold. It
provides an input voltage to the powertrain control
module (PCM). The input tells the PCM the oxygen
content of the exhaust gas (Fig. 6, 7, 8, 9, or 10). The
PCM uses this information to fine tune the air-fuel
ratio by adjusting injector pulse width. The O
2sensor produces voltages from 0 to 1 volt,
depending upon the oxygen content of the exhaust gas
in the exhaust manifold. When a large amount of
oxygen is present (caused by a lean air-fuel mixture),
the sensor produces a low voltage. When there is a
lesser amount of oxygen present (rich air-fuel mixture),
the sensor produces a higher voltage. By monitoring
the oxygen content and converting it to electrical
voltage, the sensor acts as a rich-lean switch.
Fig. 3 Testing Vacuum Diaphragm on Heated Air In- let Systems
Fig. 4 Removing Sensor Clips
Fig. 5 Air Temperature Sensor Installation
25 - 18 EMISSION CONTROL SYSTEMS Ä

The oxygen sensor contains a heating element that
keeps it at proper temperature during all operating
modes. Maintaining correct sensor temperature at all times allows the system to enter into closed loop op-
eration sooner and remain in closed loop during pe-
riods of extended idle.
In Closed Loop operation the powertrain control
module (PCM) monitors the O
2sensor input (along
with other inputs) and adjusts the injector pulse
width accordingly. During Open Loop operation the
PCM ignores the O
2sensor input. The PCM adjusts
injector pulse width based on preprogrammed (fixed)
oxygen sensor input values and the current inputs
from other sensors.
REMOVAL
CAUTION: Do not pull on the oxygen sensor wire
when disconnecting the electrical connector.
WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR.
Fig. 6 Heated Oxygen SensorÐ2.5L Engine
Fig. 7 Heated Oxygen SensorÐ2.5L MPI Engine (Flexible Fuel AA-body)
Fig. 8 Heated Oxygen SensorÐTurbo III Engine
Fig. 9 Heated Oxygen SensorÐ3.0L Engine
Fig. 10 Heated Oxygen SensorÐ3.3L/3.8L Engine
Ä EMISSION CONTROL SYSTEMS 25 - 19

(1) Disconnect oxygen sensor electrical connector.
(2) Remove sensor using Tool C-4907 (Fig. 11).
After removing the sensor, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E
tap. If reusing the original sensor, coat the sensor
threads with an anti-seize compound such as Loctite
771-64 or equivalent. New sensors have compound on
the threads and do not require additional compound.
Tighten the sensor to 27 N Im (20 ft. lbs.) torque.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
Certain vehicles equipped with either a 2.2L, 2.5L,
3.0L, 3.3L or 3.8L engines may use a back-pressure
type Exhaust Gas Recirculation (EGR) system (Fig.
12, 13, or 14). 2.5L MPI (Flexible Fuel AA-body) and
Turbo III engines do not use an EGR system. The EGR system reduces oxides of nitrogen (NOx)
in engine exhaust and helps prevent spark knock.
The system allows a predetermined amount of hot
exhaust gas to recirculate and dilute the incoming
air/fuel mixture. The diluted air/fuel mixture reduces
peak flame temperature during combustion. The EGR system consists of:
² EGR tube (connects a passage in the intake mani-
fold to the exhaust manifold)
² EGR valve
² Electronic EGR Transducer (EET)
² Connecting hoses
The electronic EGR transducer (EET) contains an
electrically operated solenoid and a back-pressure
transducer (Fig. 15). The powertrain control module
(PCM) operates the solenoid. The PCM determines
when to energize the solenoid. Exhaust system back-
pressure controls the transducer. When the PCM the solenoid, vacuum does not
reach the transducer. Vacuum flows to the trans-
ducer when the PCM de-energizes the solenoid. When exhaust system back-pressure becomes high
enough, it fully closes a bleed valve in the trans-
ducer. When the PCM de-energizes the solenoid and
back-pressure closes the transducer bleed valve, vac-
uum flows through the transducer to operate the
EGR valve. De-energizing the solenoid, but not fully closing
the transducer bleed hole (because of by low back-
pressure), varies the strength of vacuum applied to
the EGR valve. Varying the strength of the vacuum
changes the amount of EGR supplied to the engine.
This provides the correct amount of exhaust gas re-
circulation for different operating conditions.
Fig. 11 Heated Oxygen Sensor Socket
Fig. 12 EGR SystemÐ2.2L and 2.5L TBI Engines
Fig. 13 EGR SystemÐ3.0L Engines
25 - 20 EMISSION CONTROL SYSTEMS Ä

These systems do not allow EGR at idle. The 2.2L/
2.5L EGR systems operate at all temperatures. The
3.0L, 3.3L and 3.8L EGR systems do not operate
when coolant temperature is below 4.5ÉC (40É)F at
start-up. These systems activate when coolant tem-
perature reaches 77ÉC (170ÉF).
EGR SYSTEM ON-BOARD DIAGNOSTICS
The powertrain control module (PCM) performs an
on-board diagnostic check of the EGR system on all
California vehicles with EGR systems. The diagnos-
tic system uses the Electric EGR Transducer (EET)
for the system tests. The diagnostic check activates only during selected
engine/driving conditions. When the conditions are
met, the PCM energizes the transducer solenoid to
disable the EGR. The PCM checks for a change in the oxygen sensor signal. If the air-fuel mixture goes
lean, the PCM will attempt to enrichen the mixture.
The PCM registers a fault if the EGR system has
failed or degraded. After registering a fault, the PCM
turns on the malfunction indicator lamp (instrument
panel Check Engine light). The malfunction indicator
lamp indicates the need for immediate service.
If a problem is indicated by the malfunction indicator
lamp and a diagnostic trouble code for the EGR system,
check for proper operation of the EGR system. Use the
System Test, EGR Gas Flow Test and EGR Diagnosis
Chart. If the EGR system tests properly, check the sys-
tem using the DRBII scan tool. Refer to On-Board Di-
agnosis in the General Diagnosis sections of Group 14.
Also, refer to the DRBII scan tool and the appropriate
Powertrain Diagnostics Procedure manual.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
TEST
WARNING: APPLY PARKING BRAKE AND/OR
BLOCK WHEELS BEFORE PERFORMING EGR SYS-
TEM TEST.
A failed or malfunctioning EGR system can cause
engine spark knock, sags or hesitation, rough idle,
and/or engine stalling. To ensure proper operation of
the EGR system, all passages and moving parts must
be free of deposits that could cause plugging or stick-
ing. Ensure system hoses do not leak. Replace leak-
ing components. Inspect hose connections between the throttle body,
intake manifold, EGR solenoid and transducer, and
EGR valve. Replace hardened, cracked, or melted
hoses. Repair or replace faulty connectors.
Check the EGR control system and EGR valve with
the engine fully warmed up and running (engine cool-
ant temperature over 150ÉF). With the transmission in
neutral and the throttle closed, allow the engine to idle
for 70 seconds. Abruptly accelerate the engine to ap-
proximately 2000 rpm, but not over 3000 rpm. The EGR
valve stem should move when accelerating the engine
(the relative position of the groove on the EGR valve
stem should change). Repeat the test several times to
confirm movement. If the EGR valve stem moves, the
control system is operating normally. If the control sys-
tem is not operating normally, refer to the EGR Diag-
nosis Chart to determine the cause.
EGR GAS FLOW TEST
The following procedure should be used to determine
if exhaust gas is flowing through the EGR system.
Connect a hand vacuum pump to the EGR valve
vacuum motor. With engine running at idle speed,
slowly apply vacuum. Engine speed should begin to
drop when applied vacuum reaches 2.0 to 3.5 inches.
Fig. 14 EGR MountingÐ3.3L and 3.8L Engines
Fig. 15 Electric EGR Transducer (EET) Assembly
Ä EMISSION CONTROL SYSTEMS 25 - 21

GROUP TAB LOCATOR
ENGINE, CHASSIS BODY
ELECTRICAL, FUEL EMISSION SYSTEMS
WIRING DIAGRAMS
SUPPLEMENTS
Service Manual Comment Forms (Rear of Manual)

To protect the consumer from theft and possible
fraud the manufacturer is required to include a
Check Digit at the ninth position of the Vehicle Iden-
tification Number. The check digit is used by the
manufacturer and government agencies to verify the
authenticity of the vehicle and official documenta-
tion. The formula to use the check digit is not re-
leased to the general public.
BODY CODE PLATE LOCATION AND DECODING
INFORMATION
The Body Code Plate is attached to the top of the
radiator closure panel in the engine compartment.
There are seven lines of information on the body code
plate. Lines 4, 5, 6, and 7 are not used to define ser-
vice information. Information reads from left to
right, starting with line 3 in the center of the plate
to line 1 at the bottom of the plate.
BODY CODE PLATE LINE 3
DIGIT BOXES 1,2 AND 3Ð Paint Procedure
DIGIT BOXES 4 THROUGH 7Ð Primary Paint
See Group 23, Body for color codes
DIGIT BOXES 8 THROUGH 11Ð Secondary Paint
DIGIT BOXES 12 THROUGH 15Ð Interior Trim Code
DIGIT BOXES 16, 17 AND 18Ð Engine Code
² EDB = 2,5 L, 4 cylinder EFI GasÐWith Balance
Shaft
² EDF = 2.2 L, 4 cylinder EFI GasÐAutomatic or
Manual Transaxle
² EDM = 2.5 L, 4 cylinder EFI GasÐAutomatic or
Manual Transaxle
² EDN = 2.5 L, 4 cylinder EFI Flexible FuelÐAu-
tomatic Transaxle
² EDS = 2.2 L, 4 cylinder, 16 valve Turbo IIIÐMan-
ual Transaxle
² EFA = 3.0 L, V6 Gas (EFI)ÐAutomatic or Man-
ual Transaxle
² EGA = 3.3 L, V6 Gas (EFI)ÐAutomatic
² EGH = 3.8 L, V6 Gas (EFI)ÐAutomatic
BODY CODE PLATE LINE 2
DIGIT BOXES 19 THROUGH 30Ð Vehicle Order Number
DIGIT BOXES 31, 32 AND 33Ð Vinyl Roof Code
DIGIT BOXES 34, 35 AND 36Ð Vehicle Shell Car Line
² APD = Shadow
² APP = Sundance
² AAC = Lebaron Sedan
² AAD = Spirit
² AAP = Acclaim
² AGV = Daytona, IROC R/T
² AJC = LeBaron Coupe/Convertible
VIN CODE BREAKDOWN
2 INTRODUCTION Ä