cooling CHRYSLER CARAVAN 2003 Repair Manual

NOTE: Bolt torque after 1/4 turn should be over 122
N´m (90 ft. lbs.). If not, replace the bolt.
(6) Inspect push rods and replace worn or bent
rods.
(7) Install the push rods.
(8) Install the rocker arm and shaft assemblies.
(Refer to 9 - ENGINE/CYLINDER HEAD/ROCKER
ARMS - INSTALLATION)
(9) Install the cylinder head covers. (Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION)
(10) Install the exhaust manifolds. (Refer to 9 -
ENGINE/MANIFOLDS/EXHAUST MANIFOLD -
INSTALLATION)
(11) Install new O-ring on dipstick tube. Install
dipstick tube assembly (Fig. 18).
(12) Install the spark plugs.
(13) Install upper and lower intake manifolds.
(Refer to 9 - ENGINE/MANIFOLDS/INTAKE MANI-
FOLD - INSTALLATION)
(14) Fill the cooling system. (Refer to 7 - COOL-
ING - STANDARD PROCEDURE)
(15) Connect negative cable to battery.
CYLINDER HEAD COVER(S)
DESCRIPTION
The cylinder head covers are made of stamped
steel. The covers are sealed with steel reinforced sil-
icon rubber gaskets. The cylinder head cover uses
rubber isolators at each fastener location (Fig. 23).
NOTE: Due to the tight packaging near the cylinder
head covers, which makes spill clean-up difficult, a
spill during an engine oil change may be misinter-
preted as an oil leak. When investigating an oil leak
in the location of the cylinder head covers and
intake manifold, follow the procedure found in Oil
Leak Diagnosis (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING) for determining the source of a leak.
CYLINDER HEAD COVER -
RIGHT
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the wiper module. (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
REMOVAL)
(3) Disconnect spark plug wires from plugs.
(4) Disconnect PCV hose from cylinder head cover
(Fig. 24).
(5) Remove cylinder head cover bolts.
(6) Remove cylinder head cover and gasket (Fig.
23).
Fig. 21 Checking Bolts for Stretching (Necking)
1 - STRETCHED BOLT
2 - THREADS ARE NOT STRAIGHT ON LINE
3 - THREADS ARE STRAIGHT ON LINE
4 - UNSTRETCHED BOLT
Fig. 22 CYLINDER HEAD TIGHTENING SEQUENCE
Fig. 23 Cylinder Head Cover
1 - CYLINDER HEAD COVER
2 - BOLT
9 - 102 ENGINE 3.3/3.8LRS
CYLINDER HEAD (Continued)
ProCarManuals.com

(7) Position and install the connecting rod and
bearing caps on the crankshaft (Refer to 9 -
ENGINE/ENGINE BLOCK/CONNECTING ROD
BEARINGS - STANDARD PROCEDURE).
(8) Install the crankshaft rear oil seal (Refer to 9 -
ENGINE/ENGINE BLOCK/CRANKSHAFT OIL
SEAL - REAR - INSTALLATION).
(9) Install the crankshaft sprocket (Refer to 9 -
ENGINE/VALVE TIMING/TIMING CHAIN AND
SPROCKETS - INSTALLATION).
(10) Install the timing chain and camshaft
sprocket (Refer to 9 - ENGINE/VALVE TIMING/TIM-
ING CHAIN AND SPROCKETS - INSTALLATION).
(11) Install the timing chain cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING CHAIN COVER -
INSTALLATION).(12) Install the oil pick-up tube and oil pan (Refer
to 9 - ENGINE/LUBRICATION/OIL PAN - INSTAL-
LATION).
(13) Install the transaxle to the engine.
(14) Install the engine assembly (Refer to 9 -
ENGINE - INSTALLATION).
CRANKSHAFT OIL SEAL -
FRONT
REMOVAL
(1) Disconnect negative cable from battery.
(2) Raise vehicle on hoist. Remove right wheel and
inner splash shield.
(3) Remove accessory drive belt. (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL)
(4) Remove crankshaft damper. (Refer to 9 -
ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
REMOVAL)
(5) Position Special Tool 6341A on crankshaft nose.
Carefully screw the tool into the seal until it engages
firmly (Fig. 77). Be careful not to damage that crank-
shaft seal surface of cover
(6) Remove oil seal by turning the forcing screw
until the seal disengages from the cover (Fig. 78).
INSTALLATION
(1) Position Special Tool C-4992-2 Guide, on the
crankshaft nose (Fig. 79).
(2) Position new seal over the guide with the seal
spring in the direction of the engine front cover (Fig.
79).
(3) Install seal using Special Tool C-4992-1 until
seal is flush with cover. (Fig. 79).
Fig. 76 CRANKSHAFT AND BLOCK - 3.8L
1 - MAIN BEARING CAP No. 4
2 - MAIN BEARING CAP No. 3
3 - MAIN BEARING CAP No. 2
4 - MAIN BEARING CAP BOLT
5 - MAIN BEARING CAP No. 1
6 - THRUST MAIN BEARING - LOWER
7 - THRUST MAIN BEARING - UPPER
8 - MAIN BEARING CAP CROSS BOLT
9 - ENGINE BLOCK
10 - MAIN BEARING - UPPER
11 - CRANKSHAFT
12 - MAIN BEARING - LOWER
Fig. 77 Engaging Tool into Seal
1 - SEAL
2 - SPECIAL TOOL 6341A
RSENGINE 3.3/3.8L9 - 127
CRANKSHAFT (Continued)
ProCarManuals.com

VIBRATION DAMPER
REMOVAL
(1) Disconnect negative cable from battery.
(2) Raise vehicle on hoist.
(3) Remove the right front wheel and inner splash
shield.
(4) Remove the accessory drive belt. (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL)
(5) Remove vibration damper bolt.
(6) Insert Special Tool 8450 into crankshaft nose
(Fig. 83).
(7) Position 3-jaw puller Special Tool 1026 on
damper as shown in (Fig. 83). Turn puller forcing
screw until damper releases from crankshaft.
(8) Remove the crankshaft vibration damper.
INSTALLATION
(1) Install crankshaft vibration damper using the
forcing screw, nut, and thrust bearing/washer from
Special Tool 8452 (Fig. 84).NOTE: To minimize friction and prolong tool life,
lubricate the threads on the forcing screw of Spe-
cial Tool 8452.
(2) Position vibration damper on crankshaft.
(3) Screw Special Tool 8452 into crankshaft until
the bolt seats. Turn the nut to install damper until it
seats fully.
(4) Remove Special Tool 8452.
(5) Install vibration damper bolt. Torque bolt to 54
N´m (40 ft. lbs.).
(6) Install the accessory drive belt. (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION)
(7) Install inner splash shield and right front
wheel.
(8) Connect negative cable to battery.
Fig. 83 Vibration Damper - Removal
1 - SPECIAL TOOL 8450 - INSERT
2 - SPECIAL TOOL 1026-3JAWPULLER
Fig. 84 Vibration Damper - Installation
1 - FORCING SCREW / NUT FROM SPECIAL TOOL 8452
2 - VIBRATION DAMPER
3 - THRUST BEARING / WASHER
9 - 130 ENGINE 3.3/3.8LRS
ProCarManuals.com

OIL COOLER & LINES
DESCRIPTION
An engine oil cooler is used on 3.3/3.8L engines
(Heavy Duty Cooling Only) (Fig. 98). The cooler is a
coolant-to-oil type and mounted between the oil filter
and engine block.
OPERATION
Engine oil travels from the oil filter and into the
oil cooler. Engine oil then exits the cooler into the
main gallery. Engine coolant flows into the cooler
from the heater return tube and exits into the water
pump inlet.
REMOVAL
(1) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE - COOLING SYSTEM
DRAINING).
(2) Disconnect oil cooler inlet and outlet hoses
(Fig. 97).
(3) Remove oil filter.
(4) Remove oil cooler attachment fitting (Fig. 98).
(5) Remove oil cooler.
INSTALLATION
(1) Lubricate seal and position oil cooler to connec-
tor fitting on oil filter adapter (Fig. 98).NOTE: Position the flat side of oil cooler parallel to
oil pan rail.
(2) Install oil cooler attachment fitting and tighten
to 27 N´m (20 ft. lbs.) (Fig. 98).
(3) Install oil filter.
(4) Connect oil cooler inlet and outlet hoses (Fig.
97).
Fig. 96 Engine Oil Level Dipstick and Fill Locations
1 - COOLANT RECOVERY CONTAINER 3 - ENGINE OIL LEVEL DIPSTICK
2 - ENGINE OIL FILL CAP 4 - RADIATOR PRESSURE CAP
Fig. 97 Engine Oil Cooler Hoses
1 - OIL COOLER INLET TUBE
2 - INLET HOSE
3 - OIL COOLER OUTLET TUBE
4 - OUTLET HOSE
5 - WATER PUMP INLET TUBE
9 - 138 ENGINE 3.3/3.8LRS
OIL (Continued)
ProCarManuals.com

(5) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE - COOLING SYSTEM
FILLING).
OIL FILTER
REMOVAL
CAUTION: When servicing the oil filter avoid
deforming the filter can by installing the remove/in-
stall tool band strap against the can-to-base lock
seam. The lock seam joining the can to the base is
reinforced by the base plate.
(1) Using suitable oil filter wrench, turn filter
counterclockwise to remove from oil filter adapter
(Fig. 99). Properly discard used oil filter.
INSTALLATION
(1) Wipe oil filter adapter base clean and inspect
gasket contact surface.
(2) Lubricate gasket of new filter with clean
engine oil.
(3) Install new filter until gasket contacts base
(Fig. 99). Tighten filter 1 turn or 20 N´m (15 ft. lbs.).
Use filter wrench if necessary.
(4) Start engine and check for leaks.
OIL FILTER ADAPTER
REMOVAL
(1) Raise vehicle on hoist.
(2) Remove the oil filter.
(3) Disconnect oil pressure switch electrical con-
nector.
(4) Remove oil filter adapter attaching bolts (Fig.
99).
(5) Remove oil filter adapter and seal (Fig. 99).
INSTALLATION
(1) Clean oil filter adapter and install new seal.
(2) Position adapter on engine block and install
bolts (Fig. 99).
(3) Tighten adapter bolts to 28 N´m (250 in. lbs.).
(4) Connect oil pressure switch electrical connector
(Fig. 99).
(5) Install the oil filter.
(6) Lower vehicle on hoist.
(7) Start engine and allow to run approximately 2
minutes.
(8) Turn off engine and check oil level. Adjust oil
level as necessary.
Fig. 98 Engine Oil Cooler - 3.3/3.8L (Heavy Duty
Cooling)
1 - OIL FILTER ADAPTER
2 - CONNECTOR
3 - ENGINE OIL COOLER
4 - OIL COOLER ATTACHMENT FITTING
5 - OIL FILTER
Fig. 99 OIL FILTER ADAPTER
1 - SEAL
2 - OIL FILTER ADAPTER
3 - OIL FILTER
4 - BOLT
5 - OIL PRESSURE SWITCH
6 - BOLT
RSENGINE 3.3/3.8L9 - 139
OIL COOLER & LINES (Continued)
ProCarManuals.com

CAUTION: The special screws used for attaching
the EGR tube and power steering reservoir to the
manifold must be installed slowly using hand tools
only. This requirement is to prevent the melting of
material that causes stripped threads. If threads
become stripped, an oversize repair screw is avail-
able. For more information and procedure (Refer to
9 - ENGINE/MANIFOLDS/INTAKE MANIFOLD - STAN-
DARD PROCEDURE - MANIFOLD STRIPPED
THREAD REPAIR).
(7) Install the power steering reservoir (Fig. 115).
Tighten screws to manifold to 5.6 N´m (50 in. lbs.).
(8) Connect throttle and speed control cables to
throttle body (Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/THROTTLE CONTROL CABLE -
INSTALLATION)
(9) Attach make up air hose clip into the hole in
the throttle cable bracket.
(10) Connect the wiring connectors to the throttle
position sensor (TPS) and Automatic Idle Speed (AIS)
motor.
(11) Install air cleaner and air inlet hose assembly.
(12) Connect the inlet air temperature (IAT) sen-
sor electrical connector.
(13) Connect battery negative cable.
INTAKE MANIFOLD - LOWER
REMOVAL - LOWER INTAKE MANIFOLD
(1) Perform fuel system pressure release procedure
(before attempting any repairs).(Refer to 14 -
FUEL SYSTEM/FUEL DELIVERY - STANDARD
PROCEDURE)
(2) Drain the cooling system. (Refer to 7 - COOL-
ING - STANDARD PROCEDURE)
(3) Remove the upper intake manifold. (Refer to 9
- ENGINE/MANIFOLDS/INTAKE MANIFOLD -
REMOVAL)
(4) Remove the fuel line. (Refer to 14 - FUEL SYS-
TEM/FUEL DELIVERY/FUEL LINES - STANDARD
PROCEDURE) (Refer to 14 - FUEL SYSTEM/FUEL
DELIVERY/QUICK CONNECT FITTING - STAN-
DARD PROCEDURE)
(5) Remove ignition coil and bracket (Fig. 119).
(6) Disconnect heater supply hose and engine cool-
ant temperature sensor (Fig. 120).
(7) Disconnect the fuel injector wire harness.
(8) Remove the fuel injectors and rail assembly
(Fig. 119).
(9) Remove radiator upper hose.
(10) Remove the intake manifold bolts.
(11) Remove lower intake manifold (Fig. 121).WARNING: INTAKE MANIFOLD GASKET IS MADE
OF VERY THIN METAL AND MAY CAUSE PER-
SONAL INJURY, HANDLE WITH CARE.
(12) Remove intake manifold seal retainers screws
(Fig. 121). Remove intake manifold gasket.
(13) Inspect and clean manifold. (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
INSPECTION) (Refer to 9 - ENGINE/MANIFOLDS/
INTAKE MANIFOLD - CLEANING)
CLEANING
(1) Discard gasket(s).
(2) Clean all sealing surfaces.
INSPECTION
Check for:
²Damage and cracks of each section.
²Clogged water passages in end cross-overs (if
equipped).
Fig. 119 FUEL RAIL AND IGNITION COIL &
BRACKET
1 - FUEL RAIL
2 - BOLT - FUEL RAIL
3 - NUT - IGNITION COIL
4 - BOLT - IGNITION COIL
5 - IGNITION COIL
6 - BRACKET - IGNITION COIL
7 - STUD - IGNITION COIL
8 - SEPARATOR - SPARK PLUG CABLE
9 - BRACKET - SPARK PLUG CABLE SEPARATOR
10 - BOLT - SEPARATOR BRACKET
11 - BRACKET - SPARK PLUG CABLE SEPARATOR
9 - 148 ENGINE 3.3/3.8LRS
INTAKE MANIFOLD - UPPER (Continued)
ProCarManuals.com

(11) Fill the cooling system. (Refer to 7 - COOL-
ING - STANDARD PROCEDURE)
EXHAUST MANIFOLD - RIGHT
REMOVAL
(1) Disconnect battery negative cable.
(2) Remove the wiper module. (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
REMOVAL)
(3) Disconnect spark plug wires.
(4) Remove bolts fastening crossover pipe to
exhaust manifold (Fig. 124).
(5) Disconnect and remove the upstream oxygen
sensor (Fig. 127).(6) Remove the heat shield attaching screws (Fig.
127).
(7) Remove the upper heat shield (Fig. 127).
(8) Raise vehicle on hoist and remove drive belt
shield.
(9) Loosen the power steering pump support strut
lower bolt (Fig. 125).
(10) Disconnect downstream oxygen sensor connec-
tor.
(11) Disconnect catalytic converter pipe from
exhaust manifold (Fig. 126).
Fig. 123 LOWER MANIFOLD TIGHTENING
SEQUENCE
Fig. 124 CROSS-OVER PIPE
1 - CROSS-OVER PIPE
2 - BOLT
3 - GASKET
4 - FLAG NUT
Fig. 125 P/S PUMP STRUT
1 - BOLT - LOWER
2 - STRUT - P/S PUMP
3 - BOLT - UPPER
Fig. 126 Catalytic Converter to Exhaust Manifold
1 - FLAG NUT
2 - GASKET
3 - BOLT
4 - CATALYTIC CONVERTER
9 - 150 ENGINE 3.3/3.8LRS
INTAKE MANIFOLD - LOWER (Continued)
ProCarManuals.com

VALVE TIMING
STANDARD PROCEDURE
STANDARD PROCEDURE - VALVE TIMING
VERIFICATION
(1) Remove front cylinder head cover and all 6
spark plugs.
(2) Rotate engine until the #2 piston is at TDC of
the compression stroke.
(3) Install a degree wheel on the crankshaft pulley.
(4) With proper adaptor, install a dial indicator
into #2 spark plug hole. Using the indicator find TDC
on the compression stroke.
(5) Position the degree wheel to zero.
(6) Remove dial indicator from spark plug hole.
(7) Place a 5.08 mm (0.200 in.) spacer between the
valve stem tip of #2 intake valve and rocker arm pad.
Allow tappet to bleed down to give a solid tappet
effect.
(8) Install a dial indicator so plunger contacts the
#2 intake valve spring retainer as nearly perpendic-
ular as possible. Zero the indicator.
(9) Rotate the engine clockwise until the intake
valve has lifted .254 mm (0.010 in.).
CAUTION: Do not turn crankshaft any further clock-
wise as intake valve might bottom and result in
serious damage.
(10) Degree wheel should read 6 degrees BTDC to
6 degrees ATDC.
STANDARD PROCEDURE - MEASURING
TIMING CHAIN WEAR
NOTE: This procedure must be performed with the
timing chain cover removed (Refer to 9 - ENGINE/
VALVE TIMING/TIMING CHAIN COVER - REMOVAL).
(1) Position a scale next to timing chain so that
any movement of chain may be measured (Fig. 132).
(2) Position a torque wrench and socket on the
camshaft sprocket attaching bolt. Apply force in the
direction of crankshaft rotation to take up slack to
the following torque:
²41 N´m (30 ft. lb.) with cylinder heads installed
²20 N´m (15 ft. lb.) with cylinder heads removed
NOTE: With torque applied to the camshaft
sprocket bolt, crankshaft should not be permitted to
move. It may be necessary to block crankshaft to
prevent rotation.
(3) Holding a measuring scale along edge of chain
links (Fig. 132).(4) Apply force in the reverse direction to the fol-
lowing torque:
²41 N´m (30 ft. lb.) with cylinder heads installed
²20 N´m (15 ft. lb.) with cylinder heads removed
(5) Measure amount of sprocket/chain movement.
(6) Install a new timing chain and sprockets if
movement exceeds 3.175 mm (1/8 in.).
TIMING CHAIN COVER
REMOVAL
(1) Disconnect negative cable from battery.
(2) Drain cooling system. (Refer to 7 - COOLING -
STANDARD PROCEDURE)
(3) Raise vehicle on hoist.
(4) Drain engine oil.
(5) Remove right wheel and inner splash shield.
(6) Remove oil pan. (Refer to 9 - ENGINE/LUBRI-
CATION/OIL PAN - REMOVAL)
(7) Remove oil pick-up tube (Fig. 133).
(8) Remove accessory drive belt. (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL)
(9) Remove A/C compressor and set aside.
(10) Remove crankshaft vibration damper. (Refer
to 9 - ENGINE/ENGINE BLOCK/VIBRATION
DAMPER - REMOVAL)
(11) Remove radiator lower hose.
(12) Remove heater hose from timing chain cover
housing (Fig. 134) or water pump inlet tube (if
engine oil cooler equipped) (Fig. 135).
(13) Remove the right side engine mount. (Refer to
9 - ENGINE/ENGINE MOUNTING/RIGHT MOUNT
- REMOVAL)
(14) Remove idler pulley from engine bracket (Fig.
136).
(15) Remove the engine mount bracket (Fig. 136).
Fig. 132 Measuring Timing Chain Wear
1 - TORQUE WRENCH
RSENGINE 3.3/3.8L9 - 153
ProCarManuals.com

(17) Remove the water pump for cover removal
clearance. (Refer to 7 - COOLING/ENGINE/WATER
PUMP - REMOVAL)
(18) Remove the bolt attaching the power steering
pump support strut to the front cover (Fig. 137).
(19) Remove the timing chain cover fasteners.
Remove timing chain cover (Fig. 138).
INSTALLATION
(1) Be sure mating surfaces of chain case cover
and cylinder block are clean and free from burrs.
Crankshaft oil seal must be removed to insure cor-
rect oil pump engagement.
NOTE: DO NOT USE SEALER ON COVER GASKET
(2) Position new gasket on timing cover (Fig. 138).
Adhere new gasket to chain case cover, making sure
that the lower edge of the gasket is flush to 0.5 mm
(0.020 in.) passed the lower edge of the cover.
(3) Rotate crankshaft so that the oil pump drive
flats are in the vertical position.
(4) Position oil pump inner rotor so the mating
flats are in the same position as the crankshaft drive
flats (Fig. 138).
CAUTION: Make sure the oil pump is engaged on
the crankshaft correctly or severe damage may
result.
(5) Install timing cover (Fig. 138).
(6) Install timing chain cover bolts. Tighten M8
bolts to 27 N´m (20 ft. lbs.) and M10 bolts to 54 N´m
(40 ft. lbs.) (Fig. 139).
(7) Install crankshaft front oil seal. (Refer to 9 -
ENGINE/ENGINE BLOCK/CRANKSHAFT OIL
SEAL - FRONT - INSTALLATION)
(8) Install water pump and pulley. (Refer to 7 -
COOLING/ENGINE/WATER PUMP - INSTALLA-
TION)(9) Install crankshaft vibration damper. (Refer to 9
- ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
INSTALLATION)
(10) Install engine mount bracket (Fig. 136) and
tighten M10 to 54 N´m (40 ft. lbs.), M8 bolt to 28
N´m (21 ft. lb. lbs.).
(11) Install idler pulley on engine mount bracket
(Fig. 136).
(12) Install right side engine mount. (Refer to 9 -
ENGINE/ENGINE MOUNTING/RIGHT MOUNT -
INSTALLATION)
(13) Install camshaft position sensor (Refer to 8 -
ELECTRICAL/IGNITION CONTROL/CAMSHAFT
POSITION SENSOR - INSTALLATION).
(14) Connect the heater return hose at rear of tim-
ing chain cover (Fig. 134) or at water pump inlet
tube (if engine oil cooler equipped) (Fig. 135).
(15) Connect the radiator lower hose.
(16) Install A/C compressor.
(17) Install accessory drive belt. (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION)
(18) Install oil pump pick-up tube with new
O-ring. Tighten attaching bolt to 28 N´m (250 in.
lbs.).
(19) Install oil pan. (Refer to 9 - ENGINE/LUBRI-
CATION/OIL PAN - INSTALLATION)
(20) Install inner splash shield and right front
wheel.
(21) Fill crankcase with engine oil to proper level.
(22) Fill cooling system. (Refer to 7 - COOLING -
STANDARD PROCEDURE)
(23) Connect negative cable to battery.
Fig. 137 Power Steering Pump Strut
1 - BOLT - LOWER
2 - STRUT - P/S PUMP
3 - BOLT - UPPER
Fig. 138 Timing Chain Cover and Gasket
1 - GASKET
2 - TIMING CHAIN COVER
RSENGINE 3.3/3.8L9 - 155
TIMING CHAIN COVER (Continued)
ProCarManuals.com

FUEL INJECTION
OPERATION
OPERATION - INJECTION SYSTEM
All engines used in this section have a sequential
Multi-Port Electronic Fuel Injection system. The MPI
system is computer regulated and provides precise
air/fuel ratios for all driving conditions. The Power-
train Control Module (PCM) operates the fuel injec-
tion system.
The PCM regulates:
²Ignition timing
²Air/fuel ratio
²Emission control devices
²Cooling fan
²Charging system
²Idle speed
²Vehicle speed control
Various sensors provide the inputs necessary for
the PCM to correctly operate these systems. In addi-
tion to the sensors, various switches also provide
inputs to the PCM.
The PCM can adapt its programming to meet
changing operating conditions.
Fuel is injected into the intake port above the
intake valve in precise metered amounts through
electrically operated injectors. The PCM fires the
injectors in a specific sequence. Under most operat-
ing conditions, the PCM maintains an air fuel ratio
of 14.7 parts air to 1 part fuel by constantly adjust-
ing injector pulse width. Injector pulse width is the
length of time the injector is open.
The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are theprimaryinputs that determine
injector pulse width.
OPERATION - MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to 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 differ-
ent 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
programming. Inputs from the upstream and down-
stream heated oxygen sensors are not monitored dur-
ing OPEN LOOP modes, except for heated oxygensensor diagnostics (they are checked for shorted con-
ditions at all times).
During CLOSED LOOP modes the PCM monitors
the inputs from the upstream and downstream
heated oxygen sensors. The upstream heated oxygen
sensor input tells the PCM if the calculated injector
pulse width resulted in the ideal air-fuel ratio of 14.7
to one. By monitoring the exhaust oxygen content
through the upstream heated oxygen sensor, the
PCM can fine tune injector pulse width. Fine tuning
injector pulse width allows the PCM to achieve opti-
mum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation,
the following must occur:
(1) Engine coolant temperature must be over 35ÉF.
²If the coolant is over 35ÉF the PCM will wait 38
seconds.
²If the coolant is over 50ÉF the PCM will wait 15
seconds.
²If the coolant is over 167ÉF the PCM will wait 3
seconds.
(2) For other temperatures the PCM will interpo-
late the correct waiting time.
(3) O2 sensor must read either greater than 0.745
volts or less than 0.29 volt.
(4) The multi-port fuel injection systems has the
following modes of operation:
²Ignition switch ON (Zero RPM)
²Engine start-up
²Engine warm-up
²Cruise
²Idle
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
(5) The engine start-up (crank), engine warm-up,
deceleration with fuel shutoff and wide open throttle
modes are OPEN LOOP modes. Under most operat-
ing conditions, the acceleration, deceleration (with
A/C on), idle and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
²The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input. The
PCM determines basic fuel injector pulse width from
this input.
²The PCM determines atmospheric air pressure
from the MAP sensor input to modify injector pulse
width.
When the key is in the ON position and the engine
is not running (zero rpm), the Auto Shutdown (ASD)
and fuel pump relays de-energize after approximately
14 - 18 FUEL INJECTIONRS
ProCarManuals.com