AIR INJECTION SYSTEM
1988 Jeep Cherokee
1988 Exhaust Emission Systems
JEEP PULSE AIR INJECTION SYSTEM
4.2L
DESCRIPTION
Pulse air injection system is used to inject fresh air into
exhaust system. When fresh air is injected into hot exhaust gases,
combustion takes place. This reduces amount of unburned fuel that
escapes into the atmosphere.
System consists of check valves, control valves, control
valve solenoids, vacuum reservoir, vacuum lines and air lines. Pulse
air system is capable of injecting air at both catalytic converter
(downstream) or at front exhaust pipe.
OPERATION
Pulse air system uses alternating positive and negative
pressure pulsations in exhaust system to draw in fresh air through
air cleaner. Check valves are used to allow fresh air into exhaust,
but prevent exhaust from flowing back into intake system.
Air is switched between upstream and downstream injection by
2 vacuum-operated control valves. Each control valve is switched by
an electrically operated-vacuum solenoid.
Vacuum solenoids are switched on and off by MCU according to
engine operating conditions. Vacuum storage tank maintains vacuum
supply to switching solenoids.
DIAGNOSIS & TESTING
1) Check condition of all hoses and lines in system. Reroute
any kinked or restricted hoses. Repair or replace any cracked or
broken hoses. To check system operation, feel for suction in
injection hoses at air cleaner.
2) If problem exists, check to see if vacuum is being
supplied to the valve. If vacuum is not present at valve(s), check
vacuum lines or ports.
Fig. 1: Jeep Pulse Air Injection System
Courtesy of Chrysler Motors.
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