Chrysler Town & Country/Voyager, Dodge Caravan, Plymouth Voyager. Manual — part 21
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 engine
controller:
• coolant temperature
• manifold absolute pressure
• engine speed
• throttle position
• exhaust gas oxygen content
• A/C control positions
• battery voltage
The engine controller provides a ground path for the
injector to precisely control injector pulse width. The
controller energizes the injector twice per engine revo-
lution. The engine controller controls engine idle speed
and ignition timing. The engine controller controls the
air/fuel ratio according to the oxygen content in the
exhaust gas.
ACCELERATION MODE
This is a CLOSED LOOP mode. The engine control-
ler recognizes an abrupt increase in throttle position or
MAP pressure as a demand for increased engine output
and vehicle acceleration. The engine controller in-
creases injector pulse width in response to increased
fuel demand.
DECELERATION MODE
This is a CLOSED LOOP mode. During deceleration
the following inputs are received by the engine control-
ler:
• coolant temperature
• manifold absolute pressure
• engine speed
• throttle position
• exhaust gas oxygen content
• A/C control positions
• battery voltage
The engine controller may receive a closed throttle
input from the throttle position sensor (TPS) when it
senses an abrupt decrease in manifold pressure. This
indicates a hard deceleration. The engine controller
may reduce injector firing to once per engine revolu-
tion. This helps maintain better control of the air-fuel
mixture (as sensed through the O
2
sensor).
During a deceleration condition, the engine control-
ler grounds the exhaust gas recirculation (EGR) and
evaporative purge solenoids. When these solenoids are
grounded, the EGR and canister purge functions stop.
WIDE OPEN THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-
throttle operation, the following inputs are received by
the engine controller:
• coolant temperature
• manifold absolute pressure
• engine speed
• throttle position
When the engine controller senses a wide open
throttle condition through the throttle position sensor
(TPS) it will:
• De-energize the air conditioning relay. This disables
the air conditioning system.
The exhaust gas oxygen content input is not accepted
by the engine controller during wide open throttle
operation. The engine controller 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
position, the following occurs:
• All outputs are turned off.
• No inputs are monitored.
• The engine controller shuts down.
FUEL PRESSURE REGULATOR
The pressure regulator is a mechanical device lo-
cated at the top of the throttle body (Fig. 16). 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 operates, fuel flows past the injector into the
regulator. The blocked return port restricts fuel from
flowing any further. When fuel pressure reaches 270
kPa (39 PSI) it pushes on the diaphragm, compressing
the spring, and uncovers the fuel return port. The
diaphragm and spring will constantly move from an
open to closed position to keep the fuel pressure con-
stant.
Fig. 16 Fuel Pressure Regulator
.
FUEL SYSTEM
14 - 31
THROTTLE BODY
The throttle body assembly (Fig. 17) is mounted on
top of the intake manifold. It contains the fuel injector,
pressure regulator, throttle position sensor and auto-
matic idle speed 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, atomiz-
ing, and mixing fuel with the air entering the engine.
14 - 32
FUEL SYSTEM
.
Fig.
17
Throttle
Body
.
FUEL SYSTEM
14 - 33
2.5L SINGLE POINT FUEL INJECTION—GENERAL DIAGNOSIS
INDEX
page
page
60-Way Engine Controller Wiring Connector
. . . . . 43
Circuit Actuation Test Mode
. . . . . . . . . . . . . . . . . 42
Fault Code Description
. . . . . . . . . . . . . . . . . . . . . 40
General Information
. . . . . . . . . . . . . . . . . . . . . . . 34
On Board Diagnostics
. . . . . . . . . . . . . . . . . . . . . 38
State Display Test Mode
. . . . . . . . . . . . . . . . . . . . 40
Systems Test
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Throttle Body Minimum Air Flow Check
Procedure
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Visual Inspection
. . . . . . . . . . . . . . . . . . . . . . . . . 34
GENERAL INFORMATION
The fuel injection system is managed by the engine
controller. The controller receives inputs from various
switches and sensors (Fig. 1). Based on these inputs
the engine controller adjusts ignition timing and idle
speed through output devices. Refer to the Single Point
Fuel Injection section of this group for system and
component descriptions.
VISUAL INSPECTION
A visual inspection for loose, disconnected, or mis-
routed wires and hoses should be made before attempt-
ing to diagnose or service the fuel injection system. A
visual check helps save unnecessary test and diagnos-
tic time. A thorough visual inspection will include the
following checks:
(1) Check Ignition Coil Electrical Connections (Fig. 2).
Fig. 1 Throttle Body Fuel Injection Components
Fig. 2 Ignition Coil
14 - 34
FUEL SYSTEM
.
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