Exhaust Gas Recirculation (Egr) System - Toyota 4-Runner 1985 Repair Manual

EMISSION CONTROL SYSTEMS (EFI) - Exhaust Gas Recirculation (EGR) System EC-11
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
E Port
R Port
BVSV---___
~
(2)
EGR Valve EGR
EGR
Vacuum
Modulator
EC0981
EC0983
( 1 )
(3)
EGR
Vacuum
Modulator
EGR
Vacuum
Modulator
EC0982
EC0984
To reduce NOx emission, part of the exhaust gases are recirculated through the EGR valve to the intake manifold to
lower the maximum combustion temperature.
Coolant
BVSV
Throttle Valve Pressure in the EGR EGR Vacuum EGR
Exhaust Gas
Temp. Opening Angle Valve Pressure Chamber Modulator Valve
Below 30°C
CLOSED
CLOSED
Not
(86°F)
-
- -
recirculated
Positioned below
CLOSED
Not
-
-
E port recirculated
(1)
*Pressure OPENS passage
CLOSED
Not
Above 44°C
OPEN LOW constantly to atmosphere recirculated
(111°F)
Positioned between
alternating
E port & R port
(2) between low CLOSES passage
OPEN Recirculated
HIGH and high to atmosphere
Positioned above (3)
**
CLOSES passage
OPEN
Recirculated
R port HIGH to atmosphere
(increase)
Remarks:
*Pressure increase-- Modulator closes -- EGR valve opens--Pressure drops
J
~
EGR valve closes+- Modulator opens
~
* *When the throttle valve is positioned above the R port, the EGR vacuum modulator will close the at-
mosphere passage and open the EGR valve to increase the EGR gas, even if the exhaust pressure is
insufficiently low.