Feedback Systems - Jeep J-10 Series 1982 Technical & Service Manual

FUEL SYSTEMS 1J-83
FEEDBACK SYSTEMS
GENERAL
Component Replacement
Computerized Emission Control (CEC) System
(Six-Cylinder Engine)
C4 System (Four-Cylinder Engine)
Ptge
1J-87
1J-84
1J-S3
Two different feedback systems are used with Jeep
vehicles, one for four-cylinder engines and one for six-
cylinder engines. Each system is designed to achieve the
same objective: reduce undesirable exhaust emissions,
in conjunction with either a three-way catalytic (TWC)
converter or dual bed (TWC and COC) converter, while
maintaining fuel economy and good engine
performance.
With both systems, the primary feedback data is pro
vided by an oxygen sensor located in the exhaust sys
tem. This sensor provides a voltage that is proportional
to the amount of oxygen present in the exhaust gas. This
data is used by each system microprocessor to regulate
and optimize the air/fuel mixture.
The C-4 system incorporates a self-diagnostic feature
that enables service personnel to localize system
malfunctions.
C4 SYSTEM (FOUR-CYLINDER ENGINE)
This system is used with four-cylinder engines in
stalled in CJ vehicles manufactured for sale in
California.
NOTE: All reference to CJ vehicles also pertains to
Scrambler vehicles.
Electronic Control Module (ECM)
The ECM (microprocessor) is the "brains" of the C4
System. It is programmed to determine the correct air/
fuel mixture necessary for each engine operating mode.
This is accomplished via the several data inputs and the
standard data stored in the read-only-memory (ROM)
circuit.
The ECM also contains a Programmable Read Only
Memory (PROM) circuit (calibration unit) that has
stored data unique to the vehicle.
CAUTION: To ensure the internal components and
connectors do not get wet when the passenger com
partment is washed, it is advisable not spray water
directly on the ECM housing becauseit is not completely
waterproof
Oxygen Sensor
This component of the system provides a variable
voltage (100 to 900 mv) for the microprocessor (ECM)
Diagnostic Procedures For CEC System
Diagnostic Procedures For C4 System
General
System Operation
Page
1J-111
1J-83
u-ee
U-85
that is actually a voltage analog for the oxygen content
in the exhaust gas. As the oxygen content increases(lean
mixture), the voltage output from the sensor decreases
proportionally and as the oxygen content decreases (rich
mixture), the voltage output increases proportionally.
The microprocessor uses the voltage data to control the
mixture control (MC) solenoid in the model E2SE carbu
retor and maintain an optimum air/fuel mixture.
NOTE: The engine must be warmed to a pre
determined temperature before the oxygen sensor volt
age output is accepted by the microprocessor.
NOTE: The oxygen sensor must be replaced after
30,000 miles fa8 000 km) ofengine operation. The Emis
sion Maintenance lamp will be illuminated to indicate
the necessity for replacement. Refer to Chapter
1L—Engine Instrumentation for additional
information.
C4 System Data Senders
In addition to the oxygen sensor, the following data
senders are used to provide the microprocessor with
engine operation data.
•Adaptive Vacuum Switch—Closed during engine
idle and partial throttle engine operation (Adaptive
Mode of Operation).
NOTE: In the Adaptive Mode, the mixture control
(MC) solenoid is regulated to produce predetermined
air/fuel mixture ratios. During accelerationfrom idle to
partial throttle and deceleration from partial throttle to
idle the oxygen sensor cannot react fast enough to the
changes in the air/fuel mixture. As a consequence, high
HC and CO exhaust gases would be emitted momentar
ily unless the system switched to predetermined (pro
grammed) air/fuel mixture ratios.
• Wide Open Throttle (WOT) Vacuum Switch—When
a wide open throttle condition occurs, the decreased
manifold vacuum (at 5 in. Hg, 17 kPa) closes the
WOT switch, which results in the mixture control
(MC) solenoid being regulated to provide the rich
air/fuel mixture necessary for the increased airflow
(WOT Mode of Operation).
•Engine rpm (tach) Voltage from Distributor—The
mixture control (MC) solenoid is deenergized until
the voltage is equivalent to 200 rpm. The result is a
rich air/fuel mixture for engine starting (Inhibit or
Starting Mode of Operation).