Toyota 4-Runner 1985 Repair Manual page 137

I
EMISSION CONTROL SYSTEMS (CARB.) _ Air Suction and Fuel System
Feedback Control System EC-37
FEEDBACK OFF
EACV
(OFF)
Computer
Thermo
Switch
(1)
EACV
(OFF)
A03055
Vacuum
Switch
EC1099
To maintain a stoichiometric air/fuel ratio in order to simultaneously r.educe HC, CO and NOx
emissions by the
three-way catalyst, consist of the fuel system feedback control system and air suction feedback system.
*Vacuum Coolant Thermo Switch Engine Vehicle
**Ox Sensor
Switch Temp.
(1) (2)
RPM Speed Signal
EACV AS
OFF -
-
-
-
- -
Below 6°C
CLOSED OFF
(43°F)
ON
-
- -
AS
Between ON
System 18 - 44°C
- -
-
Feedback (64 - 111°F)
Always Always
Control ON
Below OPEN ON
-
System OFF Below
7 mph( 11 km/h)
Above 55°C OFF
1,000 rpm Above
(131°F)
16mph(26km/h)
RICH OPEN ON
* * *Feed
-----------
Above
LEAN CLOSED OFF
BACK
1,390 rpm
-
~ ~
*Vacuum Switch * *Ox Sensor Signal
EBCV Fuel Control System
Fuel
System OFF
-
CLOSED OFF
Feedback
Control
RICH OPEN ON
System ON
***Feedback
LEAN
CLOSED
OFF
Remarks: * By means of vacuum switch, detects heavy load driving condition.
...... Signal of air-fuel ratio of inlet gas for TWC .
... * * By means of Ox sensor, detects oxygen concentration in exhaust manifold after combusion.
If air-fuel ratio is rich for TWC, opens EACV and EBCV. If lean, closes EACV and EBCV.
--Air-fuel ratio RICH
-+
Ox sensor RICH
-+
EACV, EBCV open
~
EACV, EBCV close
+-
Ox sensor LEAN
+-
Air-fuel ratio
LEA~