Cherokee 2WD L4-150 2.5L VIN H TBI (1988)
4.0L ENGINE EGR SYSTEM
EGR System Components
The EGR system on 1988, 4.0L engines consists of the EGR valve (A), a vacuum transducer
(B)
and an EGR solenoid (C).
The vacuum transducer is controlled by exhaust back pressure. The transducer is actuated by the solenoid which in turn is operated by the ECU. The
ECU allows vacuum to flow through the solenoid when it it is not energized. A more detailed description of the transducer and solenoid functions are
provided in the MS 1700 Manual.
Vacuum lines interconnect the valve and transducer and the transducer and solenoid. The electrical portion of the solenoid is connected to the ECU.
EGR Operation
Engine vacuum flows through the EGR solenoid to the vacuum transducer (D) through connecting line (E). Vacuum flow occurs only when the solenoid
is not energized (no voltage applied).
The transducer (D) is connected to the EGR valve (F) by vacuum line (G) and back pressure line (H). The transducer is controlled by exhaust back
pressure and is ported to the exhaust manifold through line (H).
When the solenoid is not energized and exhaust gas back pressure entering EGR valve inlet (J) is high enough, back pressure holds transducer bleed
valve (K) closed. This allows vacuum to activate and operate the EGR valve.
