torque CHEVROLET DYNASTY 1993 Service Manual
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Page 1861 of 2438
tially energizes all injectors at the same time. Once
the PCM determines crankshaft position, it begins
energizing the injectors in sequence.Battery voltage is supplied to the injectors through
the ASD relay. The PCM provides the ground path
for the injectors. By switching the ground path on
and off, the PCM adjusts injector pulse width. Pulse
width is the amount of time the injector is energized.
The PCM adjusts injector pulse width based on in-
puts it receives.
IGNITION COILÐPCM OUTPUT
The auto shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing coil. When the
PCM breaks the contact, the energy in the coil pri-
mary transfers to the secondary causing the spark.
The PCM will de-energize the ASD relay if it does
not receive an input from the distributor pick-up. Re-
fer to Auto Shutdown (ASD) Relay/Fuel Pump Re-
layÐPCM Output in this section for relay operation. The ignition coil is mounted on a bracket next to
the air cleaner (Fig. 18).
PART THROTTLE UNLOCK SOLENOIDÐPCM
OUTPUT
Three-speed automatic transaxles use a part throt-
tle unlock solenoid. The PCM controls the lock-up of
the torque convertor through the part throttle unlock
solenoid. The transaxle is locked up only in direct
drive mode. Refer to Group 21 for transaxle informa-
tion.
RADIATOR FAN RELAYÐPCM OUTPUT
The radiator fan is energized by the PCM through
the radiator fan relay. The radiator fan relay is lo-
cated on the drivers side fender well near to the
PCM. The PCM grounds the relay when engine cool-
ant reaches a predetermined temperature or the air
conditioning system turns on. On AA body vehicles, the relay is located next to
the drivers side strut tower (Fig. 13). On AC, AG and AJ body vehicles, the relay is lo-
cated in the power distribution center (Fig. 12 or Fig.
14).
SPEED CONTROL SOLENOIDSÐPCM OUTPUT
The speed control vacuum and vent solenoids are
operated by the PCM. When the PCM supplies a
ground to the vacuum and vent solenoids, the speed
control system opens the throttle blade. When the
PCM supplies a ground only to the vent solenoid, the
throttle blade holds position. When the PCM removes
the ground from both the vacuum and vent solenoids,
the throttle blade closes. The PCM balances the two
solenoids to maintain the set speed. Refer to Group
8H for speed control information.
TACHOMETERÐPCM OUTPUT
The PCM supplies engine RPM to the instrument
panel tachometer through the CCD Bus. The CCD
Bus is a communications port. Various modules use
the CCD Bus to exchange information. Refer to
Group 8E for more information.
MODES OF OPERATION
As input signals to the PCM change, the PCM ad-
justs its response to the output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than for wide open
throttle (WOT). There are several different modes of
operation that determine how the PCM responds to
the various input signals. There are two different areas of operation, OPEN
LOOP and CLOSED LOOP. During OPEN LOOP modes the PCM receives in-
put signals and responds according to preset PCM
programming. Input from the oxygen (O
2) sensor is
not monitored during OPEN LOOP modes. During CLOSED LOOP modes the PCM does mon-
itor the oxygen (O
2) sensor input. This input indi-
cates to the PCM if the injector pulse width results
in an air-fuel ratio of 14.7 parts air to 1 part fuel. By
monitoring the exhaust oxygen content through the
O
2sensor, the PCM can fine tune the injector pulse
width. Fine tuning injector pulse width allows the
PCM to achieve optimum fuel economy combined
with low emissions. The 3.0L sequential MPI system has the following
modes of operation:
² Ignition switch ONÐZero-RPM
² Engine start-up
² Engine warm-up
² Cruise (Idle)
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
Fig. 18 Ignition Coil
Ä FUEL SYSTEMS 14 - 121
Page 1874 of 2438
SYSTEM TESTS
WARNING: APPLY PARKING BRAKE AND/OR BLOCK
WHEELS BEFORE PERFORMING ANY TEST ON AN
OPERATING ENGINE.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect DRBII scan tool to the data link connec-
tor located in the engine compartment near the pow-
ertrain control module (PCM). (2) Start the engine if possible, cycle the transaxle
selector and the A/Cswitch if applicable. Shut off the
engine. (3) Turn the ignition switch on, access Read Fault
Screen. Record all the fault messages shown on the
DRBII scan tool. Observe the malfunction indicator
lamp (Check Engine lamp on the instrument panel).
The lamp should light for 3 seconds then go out (bulb
check). Diagnostic trouble code erasure; access erase
diagnostic trouble code data
STATE DISPLAY TEST MODE
The switch inputs used by the powertrain control
module (PCM) have only two recognized states, HIGH
and LOW. For this reason, the PCM cannot recognize
the difference between a selected switch position ver-
sus an open circuit, a short circuit, or a defective
switch. If the change is displayed, it can be assumed
that the entire switch circuit to the PCM is functional.
From the state display screen access either State
Display Inputs and Outputs or State Display Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRBII scan tool to the vehicle. Access
the State Display screen. Then access Inputs and
Outputs. The following is a list of the engine control
system functions accessible through the Inputs and
Outputs screen. Park/Neutral Switch
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
S/C Vent Solenoid
S/C Vacuum Solenoid
A/C Clutch Relay
EGR Solenoid
Auto Shutdown Relay
Radiator Fan Relay
Purge Solenoid
Torque Converter Clutch Solenoid
Malfunction Indicator Lamp (Check Engine Lamp)
STATE DISPLAY SENSORS
Connect the DRBII scan tool to the vehicle and ac-
cess the State Display screen. Then access Sensor
Display. The following is a list of the engine control
system functions accessible through the Sensor Dis-
play screen. Battery Temperature
Oxygen Sensor Signal
Engine Coolant Temperature
Engine Coolant Temp Sensor
Throttle Position
Minimum Throttle
Battery Voltage
MAP Sensor Reading
Idle Air Control Motor Position
Adaptive Fuel Factor
Barometric Pressure
Min Airflow Idle Speed
Engine Speed
Fault #1 Key-On Info
Module Spark Advance
Speed Control Target
Fault #2 Key-on Info
Fault #3 Key-on Info
Speed Control Status
Speed Control Switch Voltage
Charging System Goal
Theft Alarm Status
Map Sensor Voltage
Vehicle Speed
Oxygen Sensor State
MAP Gauge Reading
Throttle Opening (percentage)
Total Spark Advance
CIRCUIT ACTUATION TEST MODE
The circuit actuation test mode checks for proper
operation of output circuits or devices which the pow-
ertrain control module (PCM) cannot internally rec-
ognize. The PCM can attempt to activate these
outputs and allow an observer to verify proper oper-
ation. Most of the tests provide an audible or visual
indication of device operation (click of relay contacts,
spray fuel, etc.). Except for intermittent conditions, if
a device functions properly during testing, assume
the device, its associated wiring, and driver circuit
working correctly.
OBTAINING CIRCUIT ACTUATION TEST
Connect the DRBII scan tool to the vehicle and ac-
cess the Actuators screen. The following is a list of
the engine control system functions accessible
through Actuators screens. Stop All Tests
Ignition Coil #1
Fuel Injector #1
Fuel Injector #2
Fuel Injector #3
14 - 134 FUEL SYSTEMS Ä
Page 1875 of 2438
Fuel Injector #4
Fuel Injector #5
Fuel Injector #6
Idle Air Control Motor Open/Close
Radiator Fan Relay
A/C Clutch Relay
Auto Shutdown Relay
Purge Solenoid
S/C Serv Solenoids
Generator Field
Tachometer Output
Torque Converter Clutch Solenoid
EGR Solenoid
All Solenoids/Relays
ASD Fuel System Test
Speed Control Vacuum Solenoid
Speed Control Vent Solenoid
THROTTLE BODY MINIMUM AIR FLOW CHECK
PROCEDURE
(1) Warm engine in Park or Neutral until the cool-
ing fan has cycled on and off at least once. (2) Ensure that all accessories are off.
(3) Hook-up the timing check device and tachome-
ter. (4) Disconnect the coolant temperature sensor and
set basic timing to 12É BTDC 62É BTDC.
(5) Shut off engine. Reconnect coolant temperature
sensor wire. (6) Disconnect the PCV valve hose from the PCV
valve (Fig. 4). (7) Plug the PCV valve nipple.
(8) Disconnect the idle purge hose from the vac-
uum tube under the intake manifold (Fig. 5). (9) Install Air Metering Fitting #6457 (0.125 inch
orifice) in the intake manifold mounted idle purge
hose (Fig. 6). (10) Connect DRBII scan tool.
(11) Restart the engine, allow engine to idle for at
least one minute. (12) Using the DRBII scan tool, access Min. Air-
flow Idle Speed. (13) The following will then occur:
² Idle Air Control Motor will fully close.
² Idle spark advance will become fixed.
² Engine RPM will be displayed on DRBII scan tool
(14) Check idle RPM with tachometer, if idle RPM
is within the below specification then the throttle
body min. air flow is set correctly.
(15) If idle RPM is not within specifications, shut
off the engine and clean the throttle body as follows: (a) Remove the throttle body from engine.
Fig. 4 3.0L PCV Valve
Fig. 5 3.0L Idle Purge Hose
Fig. 6 Air Metering Fitting, Special Tool 6457
IDLE SPECIFICATIONS
Ä FUEL SYSTEMS 14 - 135
Page 1878 of 2438
3.0L MULTI-PORT FUEL INJECTIONÐSERVICE PROCEDURES INDEX
page page
Idle Air Control Motor .................... 138
Canister Purge Solenoid Service ............ 143
Fuel Injector Rail Assembly ................ 139
Fuel Injectors .......................... 142
Fuel Pressure Regulator Service ............ 141
Fuel System Pressure Release Procedure ..... 138 Heated Oxygen Sensor (O
2Sensor)
......... 144
Manifold Absolute Pressure (MAP) Sensor ..... 143
PCM ................................. 143
Throttle Body ........................... 138
Throttle Body Service .................... 138
Throttle Position Sensor .................. 138
THROTTLE BODY SERVICE
(1) Disconnect negative battery cable.
(2) Remove air cleaner hose clamp to throttle body
and remove hose. (Fig. 1) (3) Remove throttle cable and transaxle linkage.
(4) Disconnect idle air control motor and throttle
position sensor (TPS) wiring connectors. (5) Disconnect vacuum hoses from throttle body.
(6) Remove throttle body to intake manifold attach-
ing nuts. Remove engine harness wiring bracket. (7) Remove throttle body and gasket.
(8) Reverse the above procedures for installation.
Tighten throttle body mounting nuts to 25 N Im (225
in. lbs.) torque.
THROTTLE BODY
When servicing body components, always assemble
components with new O-rings and seals where appli-
cable (Fig. 2). Never use lubricants on O-rings or seals,
damage may result. If assembly of component is diffi-
cult, use water to aid assembly. Use care when remov-
ing hoses to prevent damage to hose or hose nipple.
FUEL SYSTEM PRESSURE RELEASE PROCEDURE
The 3.0L MPI fuel system is under a constant
pressure of approximately 330 kPa (48 psi). Be-
fore servicing the fuel pump, fuel lines, fuel fil- ter, throttle body or fuel injectors, the fuel sys-
tem pressure must be released. (1) Loosen fuel filler cap to release fuel tank pres-
sure. (2) Disconnect injector wiring harness from engine
harness. Refer to Group 8W, Wiring Diagrams. (3) Connect one end of a jumper wire to the A142
circuit terminal of the fuel rail harness connector. (4) Connect the other end of the jumper wire to a 12
volt power source. (5) Connect one end of a jumper wire to a good
ground source. (6) Momentarily ground one of the injectors by con-
necting the other end of the jumper wire to an injector
terminal in the harness connector. Repeat procedure
for 2 to 3 injectors. (7) Continue fuel system service.
THROTTLE POSITION SENSOR
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove electrical connector from throttle posi-
tion sensor. (3) Remove throttle position sensor mounting screws
(Fig. 3). (4) Lift throttle position sensor off throttle shaft.
INSTALLATION
(1) Install throttle position sensor on throttle shaft.
Install mounting screws. Tighten screw to 2 N Im (17
in. lbs.) torque. (2) Connect electrical connector to throttle position
sensor. (3) Connect negative cable to battery.
IDLE AIR CONTROL MOTOR
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove electrical connector from idle air control
motor. (3) Remove idle air control motor mounting screws
(Fig. 4).
Fig. 1 Throttle Body
14 - 138 FUEL SYSTEMS Ä
Page 1879 of 2438
(4) Remove idle air control motor from throttle
body. Ensure the O-ring is removed with the motor.
INSTALLATION
(1) New idle air control motors have a new O-ring
installed on it. If pintle measures more than 1 inch
(25 mm) it must be retracted. Use the DRBII scan
tool Idle Air Control Motor Open/Close Test to re-
tract the pintle. (2) Carefully place idle air control motor into
throttle body. (3) Install mounting screws. Tighten screws to 2
N Im (17 in. lbs.) torque.
(4) Connect electrical connector to motor.
(5) Connect negative cable to battery.
FUEL INJECTOR RAIL ASSEMBLY
REMOVAL
WARNING: THE 3.0L MPI FUEL SYSTEM IS UNDER
A CONSTANT PRESSURE OF APPROXIMATELY 330
KPA (48 PSI). PERFORM FUEL PRESSURE RE-
LEASE PROCEDURE BEFORE SERVICING THE
FUEL RAIL OR FUEL INJECTORS.
(1) Perform the Fuel Pressure Release Procedure.
(2) Disconnect negative cable from battery.
(3) Remove air cleaner to throttle body hose.
(4) Remove throttle cable (Fig. 5).
(5) Disconnect electrical connectors from the idle
air control motor and throttle position sensor (TPS).
Fig. 2 Throttle Body 3.0L
Fig. 3 Servicing Throttle Position SensorFig. 4 Servicing Idle Air Control Motor
Ä FUEL SYSTEMS 14 - 139
Page 1881 of 2438
(18) Remove fuel rail mounting bolts. Lift fuel rail
assembly off of intake manifold.
INSTALLATION
(1) Be sure injectors are seated into the receiver
cup with lock ring in place. (2) Make sure the injector holes are clean and all
plugs have been removed. (3) To ease installation, lubricate injector O-ring
with a drop of clean engine oil. (4) Put the tip of each injector into their ports.
Push the assembly into place until the injectors are
seated in the ports. (5) Install fuel rail attaching bolts. Tighten bolts
to 13 N Im (115 in. lbs.) torque.
(6) Install fuel supply and return tube holddown
bolt and the vacuum crossover tube holddown bolt.
Tighten bolts to 10 N Im (95 in. lbs.) torque.
(7) Connect fuel injector wiring harness to engine
wiring harness. (8) Connect vacuum harness to fuel rail assembly.
(9) Remove covering from lower intake manifold
and clean surface. (10) Place intake manifold gaskets with beaded
sealer up on lower manifold. Put air intake in place.
Install ignition coil. Install attaching fasteners and
tighten to 13 N Im (115 in. lbs.) torque.
(11) Connect fuel lines to fuel rail. Tighten hose
clamps to 1 N Im (10 in. lbs.) torque.
(12) Connect vacuum harness to air intake plenum
and fuel pressure regulator. (13) Connect coolant temperature sensor electrical
connector to sensor. (14) Connect EGR tube flange to intake plenum.
Tighten mounting nuts to 22 N Im (200 in. lbs.)
torque. (15) Connect PCV and brake booster supply hose
to intake plenum. (16) Connect idle air control motor and throttle po-
sition sensor (TPS) electrical connectors. (17) Connect vacuum vapor harness to throttle
body. (18) Install throttle cable.
(19) Install air inlet hose assembly.
(20) Connect negative cable to battery.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or un-
til the ignition switch is turned to the Off position. (21) With the ignition key in ON position, access
the DRBII scan tool ASD Fuel System Test to pres-
surize the fuel system. Check for leaks.
FUEL PRESSURE REGULATOR SERVICE
REMOVAL
WARNING: THE 3.0L MPI FUEL SYSTEM IS UNDER
A CONSTANT PRESSURE OF APPROXIMATELY 330
KPA (48 PSI). PERFORM FUEL PRESSURE RE-
LEASE PROCEDURE BEFORE SERVICING THE
FUEL PRESSURE REGULATOR.
(1) Perform the Fuel Pressure Release Procedure.
(2) Disconnect negative cable from battery.
Fig. 10 Removing Air Intake Plenum
Fig. 11 Vacuum Connections at the Fuel Rail
Fig. 12 Fuel Injector Wiring Harness
Ä FUEL SYSTEMS 14 - 141
Page 1882 of 2438
(3) Loosen fuel return hose clamp and remove fuel
return hose from nipple. (4) Remove vacuum hose from fuel pressure regu-
lator. (Fig. 13). (5) Remove screw holding fuel return tube to the
intake manifold. (6) Remove fuel pressure regulator screws. Remove
fuel pressure regulator from engine.
INSTALLATION
(1) Lubricate O-ring on fuel pressure regulator
with clean 30 weight engine oil. (2) Install fuel pressure regulator into fuel rail.
Tighten screws to 10 N Im (90 in. lbs.) torque.
(3) Install screw holding fuel return tube clamp in
place. Tighten screw to 10 N Im (95 in. lbs.) torque.
(4) Connect vacuum hose to fuel pressure regula-
tor. (5) Connect fuel return hose to fuel return tube.
Tighten hose clamp to 1 N Im (10 in. lbs.) torque.
(6) Connect negative battery cable.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or un-
til the ignition switch is turned to the Off position.
(7) With the ignition key in ON position, access
the DRBII scan tool's ASD Fuel System Test to pres-
surize the fuel system. Check for leaks.
FUEL INJECTORS
WARNING: THE 3.0L MPI FUEL SYSTEM IS UNDER
A CONSTANT PRESSURE OF APPROXIMATELY 330
KPA (48 PSI). PERFORM FUEL PRESSURE RE-
LEASE PROCEDURE BEFORE SERVICING THE
FUEL INJECTORS.
REMOVAL
(1) Perform the Fuel Pressure Release Procedure.
(2) Disconnect negative cable from battery.
The fuel rail must be removed first to service the
injectors. Refer to Fuel Injector Rail Assembly Re-
moval in this section. (3) Label each injector connector with its cylinder
number. Disconnect electrical connector from injec-
tor. (4) Position fuel rail assembly so that the fuel in-
jectors are easily accessible. (5) Remove injector clip from fuel rail and injector
(Fig. 14).
(6) Pull injector straight out of fuel rail receiver
cup (Fig. 15).
Fig. 13 Fuel Pressure Regulator
Fig. 14 Fuel Injector and Rail
Fig. 15 Servicing Fuel Injector
14 - 142 FUEL SYSTEMS Ä
Page 1884 of 2438
HEATED OXYGEN SENSOR (O2SENSOR)
The oxygen sensor is installed in the exhaust man-
ifold (Fig. 21).
CAUTION: Do not pull on the oxygen sensor wires
when disconnecting the electrical connector. WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR.
(1) Disconnect oxygen sensor electrical connector.
(2) Remove sensor using Tool C-4907 (Fig. 22).
Slightly tightening the sensor can ease removal.
When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E tap.
If using original sensor, coat the threads with Loctite
771-64 anti-seize compound or equivalent. New sen-
sors are packaged with compound on the threads and
do not require additional compound. The sensor must
be tightened to 27 N Im (20 ft. lbs.) torque.
Fig. 19 PCMÐAC Body
Fig. 20 PCMÐAG and AJ Bodies
Fig. 21 Heated Oxygen Sensor
Fig. 22 Oxygen Sensor Socket
14 - 144 FUEL SYSTEMS Ä
Page 1887 of 2438
² transaxle gear selection (park/neutral switch)
The PCM also adjusts engine idle speed through
the idle air control motor based on the following in-
puts.
² brake switch
² engine coolant temperature
² engine speed (crankshaft position sensor)
² throttle position
² transaxle gear selection (park/neutral switch)
² vehicle speed
The auto shutdown (ASD) and fuel pump relays are
mounted externally, but turned on and off by the
PCM through the same circuit. The camshaft position sensor and crankshaft posi-
tion sensor signals are sent to the PCM. If the PCM
does not receive both signals within approximately
one second of engine cranking, it deactivates the
ASD and fuel pump relays. When these relays are
deactivated, power is shut off to the fuel injector, ig-
nition coil, oxygen sensor heating element and fuel
pump. The PCM contains a voltage converter that
changes battery voltage to a regulated 8.0 volts. The
8.0 volts power the camshaft position sensor, crank-
shaft position sensor and vehicle speed sensor. The
PCM also provides a 5.0 volts supply for the coolant
temperature sensor, manifold absolute pressure sen-
sor and throttle position sensor.
AIR CONDITIONING SWITCH SENSEÐPCM INPUT
When the air conditioning or defrost switch is put
in the ON position and the low pressure, high pres-
sure and ambient temperature switches are closed,
the PCM receives an input for air conditioning. After
receiving this input, the PCM activates the A/C com-
pressor clutch by grounding the A/C clutch relay.
BATTERY VOLTAGEÐPCM INPUT
The PCM monitors the battery voltage input to de-
termine fuel injector pulse width and generator field
control. If battery voltage is low the PCM will in-
crease injector pulse width.
BRAKE SWITCHÐPCM INPUT
When the brake switch is activated, the PCM re-
ceives an input indicating that the brakes are being
applied. the brake signal cancels speed control and
unlocks the torque convertor. The brake switch is
mounted on the brake pedal support bracket.
CAMSHAFT POSITION SENSORÐPCM INPUT
The camshaft position sensor provides cylinder
identification to the powertrain control module
(PCM) (Fig. 3). The sensor generates pulses as
groups of notches on the camshaft sprocket pass un-
derneath it (Fig. 4). The PCM keeps track of crank-
shaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft
sprocket. Four crankshaft pulses follow each group of
camshaft pulses.
When the PCM receives two camshaft pulses fol-
lowed by the long flat spot on the camshaft sprocket,
it knows that the crankshaft timing marks for cylin-
der one are next (on driveplate). When the PCM re-
ceives one camshaft pulse after the long flat spot on
the sprocket, cylinder number two crankshaft timing
marks are next. After 3 camshaft pulses, the PCM
knows cylinder four crankshaft timing marks follow.
One camshaft pulse after the three pulses indicates
cylinder five. The two camshaft pulses after cylinder
5 signals cylinder six (Fig. 4). The PCM can synchro-
nize on cylinders 1 or 4.
When metal aligns with the sensor, voltage goes
low (less than 0.5 volts). When a notch aligns with
the sensor, voltage spikes high (5.0 volts). As a group
of notches pass under the sensor, the voltage
switches from low (metal) to high (notch) then back
Fig. 3 Camshaft Position Sensor
Fig. 4 Camshaft Sprocket
Ä FUEL SYSTEMS 14 - 147
Page 1909 of 2438
3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐSERVICE PROCEDURES INDEX
page page
Camshaft Position Sensor Service ........... 176
Crankshaft Position Sensor ................ 176
EVAP Canister Purge Solenoid Service ....... 175
Fuel Injector ........................... 174
Fuel Injector Rail Assembly ................ 170
Fuel Pressure Regulator .................. 173
Fuel System Pressure Release Procedure ..... 169 Heated Oxygen Sensor (O
2Sensor) Service . . . 177
Idle Air Control Motor .................... 170
Manifold Absolute Pressure (MAP) Sensor ..... 175
PCM Service ........................... 175
Throttle Body ........................... 169
Throttle Body Removal ................... 169
Throttle Position Sensor .................. 169
THROTTLE BODY REMOVAL
(1) Disconnect negative battery cable.
(2) Remove the air cleaner to throttle body hose
clamp. Remove the nut holding the air cleaner as-
sembly to the air cleaner bracket. Remove the air
cleaner (Fig. 1). (3) Remove throttle and the speed control cables.
(4) Disconnect electrical connectors from the idle
air control motor and throttle position sensor (TPS). (5) Disconnect vacuum hoses from throttle body.
(6) Remove throttle body to intake manifold at-
taching nuts. (7) Remove throttle body and gasket.
(8) Reverse the above procedure for installation.
THROTTLE BODY
When servicing throttle body components, always
reassemble components with new O-rings and seals
where applicable (Fig. 2). Never use lubricants on
O-rings or seals, damage may result. If assembly of component is difficult, use water to aid assembly.
Use care when removing hoses to prevent damage to
hose or hose nipple.
FUEL SYSTEM PRESSURE RELEASE PROCEDURE
WARNING: THE 3.3L AND 3.8L MPI FUEL SYSTEMS
ARE UNDER A CONSTANT PRESSURE OF AP-
PROXIMATELY 330 KPA (48 PSI). RELEASE FUEL
SYSTEM PRESSURE BEFORE SERVICING THE
FUEL PUMP, FUEL LINES, FUEL FILTER, THROT-
TLE BODY OR FUEL INJECTORS.
(1) Disconnect negative cable from battery.
(2) Remove fuel filler cap.
(3) Remove the protective cap from the fuel pres-
sure test port on the fuel rail (Fig. 3). (4) Place the open end of fuel pressure release
hose, tool number C-4799-1, into an approved gaso-
line container. Connect the other end of hose
C-4799-1 to the fuel pressure test port. Fuel pressure
will bleed off through the hose into the gasoline con-
tainer. Fuel gauge C-4799-A contains hose C-4799-1. (5) Continue fuel system service.
THROTTLE POSITION SENSOR
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove electrical connector from throttle posi-
tion sensor. (3) Remove throttle position sensor mounting
screws (Fig. 4). (4) Lift throttle position sensor off throttle shaft.
INSTALLATION
(1) Install throttle position sensor on throttle shaft.
Install mounting screws. Tighten screw to 2 N Im (17
in. lbs.) torque. (2) Connect electrical connector to throttle position
sensor. (3) Connect negative cable to battery.Fig. 1 Throttle Body Assembly
Ä FUEL SYSTEMS 14 - 169