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25 - 6
EXHAUST GAS RECIRCULATION
Fig. 2 EXHAUST GAS RECIRCULATION
1 - EGR VALVE
2 -CHARGE AIR PRESSURE SENSOR
3 - EXHAUST MANIFOLD
4 - EGR DUCT IN CYLINDER HEAD
5 - INTAKE MANIFOLD
OPERATION
The mass of the air supplied to the cylinders per
stroke is the decisive factor for determining the opti-
mum quantity of exhaust gas for the operating con-
dition. This is calculated from the Mass Air Flow
sensor information.
The ECM evaluates this signal as well as that
from the Charge Air Pressure sensor, and outputs a
PWM signal in accordance with one of the maps
stored in it. The signal is sent to the exhaust gas
recirculation valve. The map is formulated to keep
the NOx as low as possible. The EGR valve is actu-
ated by an electric positioning motor and has a self
cleaning function. Every time the ignition switch is
turned off, the valve rotates twice to eliminate any
carbon deposits.
REMOVAL
NOTE: The EGR and EGR Cooler are serviced as an
assembly.
(1) Disconnect the negative battery cable.
(2) Partailly drain the cooling system (Refer to 7 -
COOLING/ENGINE/COOLANT - STANDARD PRO-
CEDURE).
(3) Lift up on the charge air hose retaining clip at
the intake manifold and disconnect hose with seal
(4) Disconnect the electrical connector at the EGR
positioner (Fig. 3).
(5) Disconnect the EGR cooler hose.
(6) Remove the EGR fasteners and EGR with
cooler assembly (Fig. 3).
Fig. 3 EGR VALVE
1 - EGR VALVE
2 - INTAKE MANIFOLD
3 - EGR COOLER HOSE
4 - HARNESS CONNECTOR
INSTALLATION
(1) Clean all gasket mating surfaces.
(2) Position the EGR positioner to the intake man-
ifold with a new gasket, install bolts and tighten to
124 lbs.in (14 N·m) (Fig. 3).
(3) Connect the EGR positioner electrical connec-
tor (Fig. 3).
(4) Inspect the seal of the charge air inlet tube,
replace as necessary (Fig. 3).
(5) Seat the charge air tube with gasket into the
intake manifold and push down on the charge air
tube retaining clip.
(6) Refill the cooling system (Refer to 7 - COOL-
ING/ENGINE/COOLANT
DURE).
(7) Connect negative battery cable.
VALVE COOLER
DESCRIPTION
The exhaust gas recirculation (EGR) cooler is an
integrated part of the EGR valve. Coolant flows
around the exhaust gasses, cooling them before they
are remixed with the incoming air and reburned in
the combustion chamber (Fig. 4).
VA
-
STANDARD
PROCE-
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