ESP CHEVROLET DYNASTY 1993 Owner's Guide

PISTONS: Are aluminum alloy with a steel strut,
short height, and thin wall so as to be autothermic
and light weight. The piston head with valve re-
cesses, in combination with the cylinder head, forms
a compact spherical head with clearance for total
valve lift with pistons at top dead center. The piston
skirt, top and second ring lands are finished to a ta-
pered roughness for oil retention and high resistance
to scuffing. Piston pins, press-fitted into place, join
the pistons to the connecting rods. CYLINDER HEAD: The alloy cylinder heads fea- ture cross-flow type intake and exhaust ports. Valve
guides and inserts are hardened cast iron. Valves of
heat resistance steel are arranged i
n a V with each
camshaft on center. To improve combustion speed the
chambers are a compact spherical design with a
squish area of approximately 30 percent of the piston
top area. The cylinder heads are common to either
cylinder bank by reversing the direction of installa-
tion. CAMSHAFTS: Two overhead camshafts provide
valve actuation, one front (radiator side of cylinder
bank) and one rear. The front camshaft is provided
with a distributor drive and is longer. Both cam-
shafts are supported by four bearing journals, thrust
for the front camshaft is taken at journal two and
the rear at journal three. Front and rear camshaft
driving sprockets are interchangeable. The sprockets
and the engine water pump are driven by a single
notched timing belt. ROCKER ARM SHAFTS: The shafts are retained
by the camshaft bearing journal caps. Four shafts are
used, one for each intake and exhaust rocker arm as-
sembly on each cylinder head. The hollow shafts pro-
vide a duct for lubricating oil flow from the cylinder
head to the valve mechanisms. ROCKER ARMS: Are of light weight die-cast
with roller type follower operating against the cam
shaft. The valve actuating end of the rocker arms are
machined to retain hydraulic lash adjusters, elimi-
nating valve lash adjustment. VALVES: Are made of heat resistant steel and are
further treated to resist heat. VALVE SPRINGS: Are especially designed to be
short. The valve spring wire cross-section is oval
SPECIFICATIONS
Fig. 1 Engine Identification
Ä 3.0L ENGINE 9 - 67

PISTON RINGSÐINSTALLATION
(1) The No. 1 and No. 2 piston rings have a differ-
ent cross section. Install rings with manufacturers
mark and size mark facing up, to the top of the pis-
ton (Fig. 10).
CAUTION: Install piston rings in the following or-
der:
(a) Oil ring expander.
(b) Upper oil ring side rail.
(c) Lower oil ring side rail.
(d) No. 2 Intermediate piston ring.
(e) No. 1 Upper piston ring.
(2) Install the side rail by placing one end between
the piston ring groove and the expander. Hold end
firmly and press down the portion to be installed un-
til side rail is in position. Do Not use a piston ring
expander (Fig. 11).
(3) Install upper side rail first and then the lower
side rail. (4) Install No. 2 piston ring and then No. 1 piston
ring (Fig. 12). (5) Position piston ring end gaps as shown in (Fig.
13). (6) Position oil ring expander gap at least 45É from
the side rail gaps but noton the piston pin center or
on the thrust direction. (7) Connecting rod front mark 72 must always face
forward, toward timing belt end. (Fig. 14) (8) Install the piston and connecting rod assembly
into there respective bore from the cylinder block
top.
CAUTION: Piston assemblies are not to be inter-
changed from bank to bank.
(9) Check alignment marks made during disassem-
bly and that bearing position notches new or used
are on the same side as shown in (Fig. 15).
CONNECTING ROD CLEARANCE
(1) Following procedures specified in the Standard
Service Procedures Section for Measuring Main Bear-
ing Clearance and Connecting Rod Bearing Clear-
ance. (Fig. 16). Refer to (Fig. 18) for specifications.
Fig. 10 Piston Ring Installation
Fig. 11 Installing Side Rail
Fig. 12 Installing Upper and Intermediate Rings
Fig. 13 Piston Ring End Gap Position
9 - 84 3.0L ENGINE Ä

CYLINDER HEADS: Cylinder heads incorporate
valve shrouding to create turbulence-producing com-
bustion chambers, described as fast burn. Valve seat
and guides are inserts. A steel flanged composition
type gasket is used between head and block. VALVE COVERS: The covers are sealed with
steel reinforced silicon rubber gaskets. INTAKE MANIFOLD: The intake manifold is a
tuned two-piece semi-permanent mold aluminum casting with individual primary runners leading
from a plenum to the cylinders. The manifold is de-
signed to boost torque in the 3600 rpm range and
contributes to the engine's broad, flat torque curve,
which was desired for excellent engine tractability,
response and usable power output. The intake manifold is also cored with upper level
EGR passages for balanced cylinder to cylinder EGR
distribution. VALVE TRAIN: Valve train design incorporates
the use of hydraulic roller tappets. Rocker arms are
installed on a rocker arm shaft attached to the cylin-
der head with four bolts and retainers. Viton valve
stem seals provide valve sealing. Conventional type
pushrods, retainers and valve stem locks are used.
Unique beehive style valve spring are used with
lightweight retainers for improved high RPM perfor-
mance. EXHAUST MANIFOLDS: Exhaust manifolds are
log type with a crossover and is attached directly to
the cylinder heads.ENGINE MOUNTS
REMOVAL AND INSTALLATION
RIGHT SIDE MOUNT
(1) Remove the right engine mount insulator ver-
tical fasteners from frame rail. (2) Remove the load on the engine motor mounts
by carefully supporting the engine and transmission
assembly with a floor jack.
Fig. 1 3.3/3.8L V-6 Engine
Fig. 2 Engine Identification
Ä 3.3/3.8L ENGINE 9 - 99

(15) Install rocker arm covers tighten screws to 14
N Im (120 in. lbs.) and connector to ignition coils.
(16) Install Intake Manifold; Refer to Intake Mani-
fold Installation 3.3/3.8L Engine, Group 11 Exhaust
System and Intake Manifold.
HYDRAULIC TAPPETS
The valve train includes roller tappet assemblies,
aligning yokes and yoke retainer. Roller tappet alignment is maintained by machined
flats on tappet body being fitted in pairs into six
aligning yokes. The yokes are secured by an alignment
yoke retainer (Fig. 26).
PRELIMINARY STEP TO CHECKING THE HY- DRAULIC TAPPETS
Before disassembling any part of the engine to cor-
rect tappet noise, read the oil pressure at the gauge.
Install a reliable gauge at pressure sending unit if
vehicle has no oil pressure gauge and check the oil level
in the oil pan. The pressure should be between 30 and
80 psi (206.8 to 551.6 kPa) at 2000 rpm. The oil level in the pan should never be above the
MAX mark on dipstick, or below the MIN mark. Either
of these two conditions could be responsible for noisy
tappets. Oil Level Check: stop engine after reach-
ing normal operating temperature . Allow 5 min-
utes to stabilize oil level, check dipstick.
OIL LEVEL TOO HIGH
If oil level is above the MAX mark on dip stick, it is
possible for the connecting rods to dip into the oil while
engine is running and create foam. Foam in oil pan
would be fed to the hydraulic tappets by the oil pump
causing them to become soft and allow valves to seat
noisily.
OIL LEVEL TOO LOW
Low oil level may allow pump to take in air which
when fed to the tappets, causes them to become soft
and allows valves to seat noisily. Any leaks on intake
side of pump through which air can be drawn will
create the same tappet action. Check the lubri- cation system from the intake strainer to the pump
cover, including the relief valve retainer cap. When
tappet noise is due to aeration, it may be intermittent
or constant, and usually more than one tappet will be
noisy. When oil level and leaks have been corrected,
engine should be operated at fast idle to allow all of the
air inside of the tappets to be bled out.
VALVE TRAIN NOISE DIAGNOSIS
To determine source of valve train noise, operate
engine at idle with cylinder head covers removed and
listen for source of the noise. Worn valve guides or cocked springs are some-
times mistaken for noisy tappets. If such is the
case, noise may be dampened by applying side
thrust on the valve spring. If noise is not appre-
ciably reduced, it can be assumed the noise is in
the tappet. Inspect the rocker arm push rod
sockets and push rod ends for wear. Valve tappet noise ranges from light noise to a heavy
click. A light noise is usually caused by excessive
leakdown around the unit plunger which will necessi-
tate replacing the tappet, or by the plunger partially
sticking in the tappet body cylinder. A heavy click is
caused either by a tappet check valve not seating, or by
foreign particles becoming wedged between the
plunger and the tappet body causing the plunger to
stick in the down position. This heavy click will be
accompanied by excessive clearance between the valve
stem and rocker arm as valve closes. In either case,
tappet assembly should be removed for inspection and
cleaning.
TAPPET REMOVAL
(1) Refer to Cylinder Head Removal of this section to
remove intake manifold and cylinder heads for access
to tappets for service. (2) Remove yoke retainer and aligning yokes.
(3) Use Tool C-4129 to remove tappets from their
bores. If all tappets are to be removed, identify tappets
to insure installation in original location. If the tappet or bore in cylinder block is scored,
scuffed, or shows signs of sticking, ream the bore
to next oversize and replace with oversize tap-
pet.
CAUTION: The plunger and tappet bodies are not
interchangeable. The plunger and valve must always
be fitted to the original body. It is advisable to work on
one tappet at a time to avoid mixing of parts. Mixed
parts are not compatible. Do not disassemble a tap-
pet on a dirty work bench.
DISASSEMBLY (FIG. 27)
(1) Pry out plunger retainer spring clip.
Fig. 26 Roller Tappets Aligning Yoke and Retainer
9 - 108 3.3/3.8L ENGINE Ä

with a minimum octane of 87 may be used. However,
the use of lower octane gasoline will result in re-
duced performance.
FLEXIBLE FUEL AA-BODY VEHICLES
These vehicles will operate on either unleaded gas-
oline with a minimum posted octane of 87 or M85
fuel. M85 fuel is a mixture of 85 percent methanol
and 15 percent unleaded gasoline. The vehicle also
will operate on mixture of M85 and unleaded gaso-
line with a minimum posted octane of 87. Do not
use 100 percent methanol in these vehicles.
THE FOLLOWING IS APPLICABLE TO ALL VEHICLES
Light spark knock at low engine speeds is not
harmful to your engine. However, continued heavy
spark knock at high speeds can cause damage and
should be reported to your dealer immediately. En-
gine damage resulting from operating with a heavy
spark knock may not be covered by the new vehicle
warranty. In addition to using unleaded gasoline with the
proper octane rating, gasolines that contain deter-
gents, corrosion and stability additives are recom-
mended. Using gasolines that have these additives
will help improve fuel economy, reduce emissions,
and maintain vehicle performance. Generally, pre-
mium unleaded gasolines contain more additive than
regular unleaded. Poor quality gasoline can cause problems such as
hard starting, stalling, and stumble. If you experi-
ence these problems, try another brand of gasoline
before considering service for the vehicle.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend gasoline with materials
that contain oxygen such as alcohol, MTBE (Methyl
Tertiary Butyl Ether) and ETBE (Ethyl Tertiary Bu-
tyl Ether). The type and amount of oxygenate used
in the blend is important. The following are generally used in gasoline
blends: Ethanol - (Ethyl or Grain Alcohol) properly blended, is used as a mixture of 10 percent ethanol
and 90 percent gasoline. Gasoline blended with eth-
anol may be used in your vehicle. Methanol - (Methyl or Wood Alcohol) is used in a
variety of concentrations when blended with un-
leaded gasoline. You may find fuels containing 3 per-
cent or more methanol along with other alcohols
called cosolvents. Do not use gasolines containing Methanol.
Use of methanol/gasoline blends may result in
starting and driveability problems and damage criti-
cal fuel system components. Problems that are the result of using methanol/gas-
oline blends are not the responsibility of Chrysler
Motors and may not be covered by the new vehicle
warranty. MTBE/ETBE - Gasoline and MTBE (Methyl Ter-
tiary Butyl Ether) blends are a mixture of unleaded
gasoline blended and up to 15 percent MTBE. Gaso-
line and ETBE (Ethyl Tertiary Butly Ether) are
blends of gasoline and up to 17 percent ETBE. Gas-
oline blended with MTBE or ETBE may be used in
your vehicle. Clean Air Gasoline
Many gasolines are now being blended that con-
tribute to cleaner air, especially in those areas of the
country where pollution levels are high. These new
blends provide a cleaner burning fuel and some are
referred to as reformulated gasoline. In areas of the country where carbon monoxide lev-
els are high, gasolines are being treated with oxy-
genated materials such as ETBE, MTBE and
ethanol. The use of gasoline blended with these ma-
terials also contributes to cleaner air. Chrysler Corporation supports these efforts toward
cleaner air and recommends that you use these gas-
olines as they become available. Materials Added to Fuel
Indiscriminate use of fuel system cleaning agents
should be avoided. Many of these materials intended
for gum and varnish removal may contain active sol-
vents of similar ingredients that can be harmful to
fuel system gasket and diaphragm materials.
14 - 2 FUEL SYSTEMS Ä

(1) Loosen fuel filler cap to release fuel tank pres-
sure. (2) Disconnect injector wiring harness connector at
edge of throttle body (Fig. 4). (3) Connect a jumper wire between terminal Num-
ber 1 of the injector harness and engine ground. (4) Connect a jumper wire to the positive terminal
Number 2 of the injector harness and touch the bat-
tery positive post for no longer than 5 seconds .
This releases system pressure. (5) Remove jumper wires.
(6) Continue fuel system service.
FUEL SYSTEM PRESSURE RELEASE
PROCEDUREÐ3.0L
(1) Disconnect the fuel rail electrical harness from
the engine harness. Refer to Group 8W, Wiring Dia-
grams. (2) Connect one end of a jumper wire to the A142
circuit terminal of the fuel rail harness connector. (3) Connect the other end of the jumper wire to a
12 volt power source. (4) Connect one end of a jumper wire to a good
ground source. (5) Momentarily ground one of the injectors by
connecting the other end of the jumper wire to an in-
jector terminal in the harness connector. Repeat pro-
cedure for 2 to 3 injectors.
FUEL PUMP ASSEMBLY
The fuel pump assembly consists of the fuel pump
and the reservoir body. The reservoir body takes the place of an internal
fuel tank reservoir. The reservoir maintains fuel at
the pump inlet during all driving conditions, espe-
cially when the fuel level is low. The system uses a positive displacement, gerotor
gear, immersible pump with a permanent magnet
electric motor (Fig. 5). The pump draws fuel through
a strainer and pushes it through the electric motor to
the outlet. The pump contains three check valves.
One valve relieves internal fuel pump pressure and
regulates maximum pump output. Another valve, in-
side the pump assembly in the fuel return circuit,
prevents fuel tank leakage if the line is damaged
during an accident. The third valve, in the pump out-
let, maintains pump pressure during engine off con-
ditions. The fuel pump relay provides voltage to the
fuel pump. All pumps have a maximum stall pres-
sure output of approximately 930 kPa (135 psi). All front wheel drive car fuel systems, except
Turbo III and flexible fuel AA-body vehicles use the
same fuel pump. Turbo III and flexible fuel AA-Body
vehicles each use different fuel pumps although they
look similar to pumps used in other vehicles. Release fuel system pressure before servicing the
fuel tank, fuel pump, fuel lines, fuel filter, or parts of
the fuel rail. Follow the Fuel System Pressure Re-
lease procedure to relieve fuel system pressure.
Fig. 2 Fuel Pressure Test PortÐTypical
Fig. 3 Releasing Fuel PressureÐEngines With Test Ports On Fuel Rail
Fig. 4 Injector Harness ConnectorÐ2.2L/2.5L TBI
Ä FUEL SYSTEMS 14 - 5

INSTALLATION
WARNING: FUEL TANKS DESIGNED FOR GASO-
LINE ONLY VEHICLES CANNOT BE USED ON
FLEXIBLE FUEL AA-BODY VEHICLES. WHEN SER-
VICING THE FUEL SYSTEM OF A FLEXIBLE FUEL
VEHICLE, ONLY USE ORIGINAL EQUIPMENT OR
EQUIVALENT REPLACEMENT COMPONENTS. (1) Position fuel tank on transmission jack. Con-
nect vapor separator/rollover valve hose and position
insulator pad on fuel tank. Position vapor vent so
that it is not pinched between tank and floor pan
during installation. (2) Raise tank and fuel filler tube carefully into
position. Use a light coating of power steering fluid
to ease fuel filler tube installation. Ensure filler tube
grommet is not damaged. Verify that the tube is in-
stalled correctly. (3) Tighten fuel tank strap nuts to 23 N Im (250 in.
lbs.) torque. Remove transmission jack. Ensure
straps are not twisted or bent. (4) Lubricate the metal tubes on the fuel pump
with clean 30 weight engine oil. Install the quick
connect fuel fittings. Refer to Quick Connect Fittings
in the Fuel Delivery section of this Group. (5) Attach electrical connector to fuel pump mod-
ule and level sensor unit. (6) Lower the vehicle.
(7) Attach filler tube to filler neck opening in
quarter panel. Tighten quarter panel screws to 2
N Im (17 in. lbs.) torque.
(8) Fill fuel tank, install filler cap, and connect
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.
(9) Use the DRBII scan tool ASD Fuel System Test
to pressurize the fuel system. Check for leaks.
FUEL PUMP MODULE
Refer to the Fuel Delivery section of this group.
METHANOL CONCENTRATION SENSOR
Refer to the Fuel Delivery section of this group.
FUEL RESERVOIR
The fuel reservoir is internal to the fuel pump as-
sembly (Fig. 6). The purpose is to provide fuel at the
fuel pump intake during all driving conditions, espe-
cially when low fuel levels are present.
FUEL TANK LEVEL SENSOR
DIAGNOSIS
This procedure test the resistance of the level sen-
sor itself. It does not test the level sensor circuit. Re-
fer to Group 8W, Wiring Diagrams for circuit
identification and Group 8E, Instrument Panel and
Gauges for fuel gauge information. The level sensor is a variable resistor. Its resis-
tance changes with the amount of fuel in the tank.
The float arm attached to the sensor moves as the
fuel level changes. To test the level sensor, connect
an ohmmeter across the sensor signal and sensor
ground terminals of the fuel level sensor connector
(Fig. 7 or Fig. 8). Move the float lever to the full stop
and empty stop positions shown in the resistance
chart (Fig. 7 or Fig. 8). Record the resistance at each
point. Replace the level sensor if the resistance is not
within specifications. The low fuel warning light specifications determine
if the level sensor portion of the warning light circuit
functions properly. It does not test the complete
warning light circuit. Refer to Group 8W, Wiring Diagrams for circuit
identification and Group 8E, Instrument Panel and
Gauges for fuel gauge information.
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
Fig. 6 Fuel Reservoir
14 - 18 FUEL SYSTEMS Ä

TACHOMETERÐPCM OUTPUT
The PCM supplies engine RPM to the instrument
panel tachometer. Refer to Group 8 for tachometer
information.
MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to the output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does 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 input
signals and responds according to preset PCM pro-
gramming. Input from the oxygen (O
2) sensor is not
monitored during OPEN LOOP modes. During CLOSED LOOP modes, the PCM does moni-
tor the oxygen (O
2) sensor input. This input tells the
PCM if the calculated injector pulse width results in an
air-fuel ratio of 14.7 to 1. By monitoring the exhaust
oxygen content, the can PCM fine tune injector pulse
width for optimum fuel economy and low emissions. The single point fuel injection system has the follow-
ing modes of operation:
² Ignition switch ON - Zero RPM
² Engine start-up
² Engine warm-up
² Cruise (Idle)
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
The engine start-up (cranking), engine warm-up, and
wide open throttle modes are OPEN LOOP modes. The
acceleration, deceleration, and cruise modes, with the
engine at operating temperature are CLOSED
LOOP modes (under most operating conditions).
IGNITION SWITCH ON (ZERO RPM) MODE
When the single point fuel injection system is acti-
vated by the ignition switch, the following actions
occur:
² The PCM determines atmospheric air pressure from
the MAP sensor input to calculate basic fuel strategy.
² The PCM monitors the coolant temperature sensor
and throttle position sensor inputs. The PCM modifies
fuel strategy based on these inputs. When the key is in the ON position and the engine is
not running, the (ASD) and fuel pump relays are not
energized. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injector or oxygen
sensor heating element. ENGINE START-UP MODE
This is an OPEN LOOP mode. The following actions
occur when the starter motor is engaged. If the PCM receives a distributor signal it energizes
the auto shutdown (ASD) relay and fuel pump relay to
supply battery voltage to the fuel injector, ignition coil
and oxygen sensor heating element. If the PCM does
not receive a distributor input, it de-energizes the ASD
and fuel pump relays after approximately one second. When the engine idles within 664 RPM of the target
RPM, the PCM compares the current MAP value with
the atmospheric pressure value it received during the
Ignition Switch On (Zero RPM) Mode. If a minimum
difference between the two is not detected, a MAP
sensor fault is set into memory. Once the ASD relay and fuel pump relay have ener-
gized, the PCM:
² Supplies a ground path to the injector. The injector
is pulsed four times per engine revolution instead of
the normal two pulses per revolution.
² Determines injector pulse width based on coolant
temperature, MAP sensor input, throttle position, and
the number of engine revolutions since cranking was
initiated.
² Monitors the coolant temperature sensor, distribu-
tor pick-up, MAP sensor, and throttle position sensor to
determine correct ignition timing.
ENGINE WARM-UP MODE
This is a OPEN LOOP mode. The following inputs
are received by the PCM:
² coolant temperature
² manifold absolute pressure (MAP)
² engine speed (distributor pick-up)
² throttle position
² A/C switch
² battery voltage
The PCM provides a ground path for the injector to
precisely control injector pulse width (by switching the
ground on and off) and fires the injector twice per
engine revolution. The PCM regulates ignition timing.
It also adjusts engine idle speed through the idle air
control motor.
CRUISE OR IDLE MODE
When the engine is at operating temperature this is
a CLOSED LOOP mode. During cruising speed and at
idle the following inputs are received by the PCM:
² coolant temperature
² manifold absolute pressure
² engine speed
² throttle position
² exhaust gas oxygen content
² A/C control positions
² battery voltage
14 - 32 FUEL SYSTEMS Ä

The PCM provides a ground path for the injector to
precisely control injector pulse width and fires the in-
jector twice per engine revolution. The PCM controls
engine idle speed and ignition timing. The PCM con-
trols the air/fuel ratio according to the oxygen con-
tent in the exhaust gas.
ACCELERATION MODE This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
DECELERATION MODE This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
² coolant temperature
² manifold absolute pressure
² engine speed
² throttle position
² exhaust gas oxygen content
² A/C control positions
² battery voltage
The PCM may receive a closed throttle input from
the throttle position sensor (TPS) at the same time it
senses an abrupt decrease in manifold pressure from
the manifold absolute pressure (MAP) sensor. This
indicates a hard deceleration. The PCM may reduce
injector firing to once per engine revolution. This
helps maintain better control of the air-fuel mixture
(as sensed through the O
2sensor).
During a deceleration condition, the PCM grounds
the exhaust gas recirculation transducer (EET) sole-
noid. EGR stops when the PCM grounds the solenoid.
WIDE OPEN THROTTLE MODE This is an OPEN LOOP mode. During wide open
throttle operation, the following inputs are received
by the PCM:
² coolant temperature
² manifold absolute pressure
² engine speed
² throttle position
When the PCM senses a wide open throttle condi-
tion through the throttle position sensor (TPS) it
will:
² De-energize the air conditioning relay. This dis-
ables the air conditioning system.
² Provide a ground path for the electric EGR trans-
ducer (EET) solenoid, preventing the EGR system
from functioning. The exhaust gas oxygen content input is not ac-
cepted by the PCM during wide open throttle opera- tion. The PCM will adjust injector pulse width to
supply a predetermined amount of additional fuel.
IGNITION SWITCH OFF MODE
When the ignition switch is turned to the OFF po-
sition, the following occurs:
² All outputs are turned off.
² No inputs are monitored.
² The PCM shuts down.
FUEL PRESSURE REGULATOR
The pressure regulator is a mechanical device lo-
cated at the top of the throttle body (Fig. 17). Its
function is to maintain a constant 270 kPa (39 PSI)
across the fuel injector tip.
The regulator uses a spring loaded rubber dia-
phragm to uncover a fuel return port. When the fuel
pump becomes operational, fuel flows past the injec-
tor into the regulator, and is restricted from flowing
any further by the blocked return port. When fuel
pressure reaches 270 kPa (39 PSI) it pushes on the
diaphragm, compresses the spring, and uncovers the
fuel return port. The diaphragm and spring con-
stantly move from an open to closed position keeping
fuel pressure consistent.
THROTTLE BODY
The throttle body assembly (Fig. 18) is mounted on
top of the intake manifold. It contains the fuel injec-
tor, pressure regulator, throttle position sensor and
idle air control motor. Air flow through the throttle
body is controlled by a cable operated throttle blade
located in the base of the throttle body. The throttle
body itself provides the chamber for metering, atom-
izing, and mixing fuel with the air entering the en-
gine.
Fig. 17 Fuel Pressure Regulator
Ä FUEL SYSTEMS 14 - 33

mode, the PCM compensates for the failure of certain
components that send incorrect signals. The PCM
substitutes for the incorrect signals with inputs from
other sensors and by using stored default values.Signals that can trigger the Malfunction Indi-
cator (Check Engine) Lamp.
² An emission system component
² Battery Voltage Input
² Charging system
² Engine Coolant Temperature Sensor
² Manifold Absolute Pressure Sensor
² Methanol Concentration Sensor
² Throttle Position Sensor
The malfunction indicator lamp can also display
diagnostic trouble codes. Cycle the ignition switch on,
off, on, off, on, within five seconds and the PCM
displays any diagnostic trouble codes stored in
memory. Refer to the 2.5L Flexible Fuel Multi-Port
Fuel InjectionÐOn Board Diagnostics section in this
group for diagnostic trouble code descriptions.
RADIATOR FAN RELAYÐPCM OUTPUT
The radiator fan is energized by the PCM through
the radiator fan relay. The PCM grounds the radiator
fan relay when engine coolant reaches a predetermined
temperature. For more information, refer to Group 7,
Cooling Systems. The radiator fan relay is mounted on the drivers side
fender well, next to the strut tower (Fig. 11).
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 sole-
noids 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. Refer to Group 8 for tachometer
information.
TORQUE CONVERTER CLUTCH SOLENOIDÐPCM
OUTPUT
Three-speed automatic transaxles use a torque con-
verter clutch solenoid. The PCM controls the lock-up of
the torque convertor through the solenoid. The tran-
saxle is locked up only in direct drive mode. Refer to
Group 21 for transaxle information.
MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to the output devices. For example, the PCM must calculate a different injector pulse
width and ignition timing for idle than it does 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 input
signals and responds according to preset PCM pro-
gramming. Input from the oxygen (O
2) sensor is not
monitored during Open Loop modes. During CLOSED LOOP modes, the PCM does moni-
tor the oxygen (O
2) sensor input. The input indicates if
the calculated injector pulse width results in the ideal
air-fuel ratio for the current percentage of methanol in
the fuel. By monitoring the exhaust oxygen content
through the O
2sensor, the PCM can fine tune the
injector pulse width to achieve optimum fuel economy
combined with low emissions. The 2.5L flexible fuel multi-port fuel injection system
has the following modes of operation:
² Ignition switch ON - Zero RPM
² Engine start-up
² Engine warm-up
² Cruise (Idle)
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
The engine start-up (crank), engine warm-up, and
wide open throttle modes are OPEN LOOP modes. The
acceleration, deceleration, and cruise modes, with the
engine at operating temperature are CLOSED
LOOP modes (under most operating conditions).
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch cycles and past the On
position, the fuel injection system activates and the
following actions occur:
² For two seconds at key ON (and during cranking),
the methanol concentration sensor calibrates the PCM.
During the calibration period the sensor sends 4.45
volts to the PCM as a correction factor. After the
calibration period, the methanol concentration sensor
output represents the methanol percentage in the fuel.
² The PCM calculates basic fuel strategy by determin-
ing atmospheric air pressure from the MAP sensor
input.
² The PCM monitors the coolant temperature sensor
and throttle position sensor input. The PCM modifies
fuel strategy based on this input. When the key is in the ON position and the engine is
not running, the auto shutdown (ASD) relay and fuel
pump relay are not energized. Therefore battery volt-
age is not supplied to the fuel pump, ignition coil, fuel
injector or oxygen sensor heating element.
Ä FUEL SYSTEMS 14 - 63