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

EC-30
EMISSION CONTROL SYSTEMS (CARB.) - Exhaust Gas Recirculation (EGR) System
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
(Federal and Canad~ \
(1)
EGR Vacuum
R Port
Modulator
EGR Valve
BVSV
R Port
P Port
..
~;
Constant Pressure Chamber
EC0328 EC0329
(2)
(3)
A03048
R Port
R Port
BVSV (Open)
Constant Pressure Chamber
Constant Pressure Chamber
EC0330
EC0331
To reduce i'JOx 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
-
-
-
recirculated
(86°F)
(J-K)
Positioned below
CLOSED
Not
- -
EGR port
recirculated
( 1 )
*Pressure
OPENS passage
CLOSED
Not
Above 44°C
OPEN
I
LOW constantly to atmosphere recirculated
Positioned between
(111°F)
(J-K)
P port & R port
alternating
(2) between low CLOSES passage
OPEN
Recirculated
HIGH and high
to atmosphere
I
Positioned above
(3)
**
CLOSES passage
OPEN
Recirculated
EGR R port HIGH to atmosphere
(increase)
Remarks: *Pressure increase--Modulator closes--EGR valve opens--Pressure drOps]
... 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.