Chrysler DODGE D150 1993 Service Manual page 1489

25 - 12 EMISSION CONTROL SYSTEMS
EGR DIAGNOSIS CHART
NOTE: ALL TESTS MUST BE M A D E WITH FULLY W A R M ENGINE R U N N I N G
CONTINUOUSLY FOR AT LEAST T W O MINUTES
W A R N I N G : BE SURE TO APPLY P A R K I N G BRAKE A N D / O R B L O C K WHEELS BEFORE PERFORMING
IDLE CHECK O R ADJUSTMENT, O R A N Y ENGINE R U N N I N G TESTS O R ADJUSTMENTS.
Condition
Possible Cause Correction
EGR VALVE STEM
DOES NOT M O V E O N
SYSTEM TEST.
(a) Cracked, leaking, disconnected or
plugged hoses.
EGR VALVE STEM
DOES NOT M O V E O N
SYSTEM TEST.
OPERATES N O R M A L L Y
O N EXTERNAL
V A C U U M SOURCE.
ENGINE WILL NOT
IDLE. DIES OUT O N
RETURN TO IDLE O R
IDLE IS VERY R O U G H
OR S L O W .
(a) Defective control system—Plugged passages.
(b) Defective control system—solenoid or solenoid
control circuit,
(a) High EGR valve leakage in closed
position.
(b) EGR tube to intake manifold leak.
(c) Solenoid or control signal to solenoid failure.
(a)
(b)
(a)
(b)
(a)
Verify correct hose connections and leak
check and confirm that alt hoses are open.
If defective hoses are found, replace hose
harness.
Disconnect hose harness from EGR vacuum
transducer and connect auxiliary vacuum
supply. Raise engine rpm to 2000 rpm and
hold. Apply 10" Hg vacuum while checking
valve movement. If no valve movement oc­
curs, replace valve/transducer assy. If valve
opens (approx. 3mm or 1/8" travel), hold
supply vacuum to check for diaphragm
leakage. Valve should remain open 30
seconds or longer. If leakage occurs, replace
valve/transducer assy. If valve is satisfac­
tory, check control system.
Remove throttle body and inspect port (slot
type) in throttle bore and associated
passage in throttle body. Use suitable sol­
vent to remove deposits and check for flow
with light air pressure. Normal operation
should be restored to EGR system.
Refer to Group 14. General Diagnosis "On
Board Diagnostics" to check solenoid.
If removal of vacuum hose from EGR valve
does not correct rough idle,
(a 1) Turn engine off. Remove the air cleaner ex­
posing the inlet to the throttle body.
(a2) Disconnect the backpressure hose from the
EGR valve.
(a3) Using a nozzle with a rubber grommet con­
nection, direct compressed air (50 to 60 psi)
down through the steel backpressure tube on
the EGR valve while opening and closing the
throttle blade.
(a4) If the sound from the compressed air changes
distinctly in step a3, the poppet is leaking
and air is entering the intake manifold.
Replace the EGR valve.
Remove tube and visually inspect tube seal
on gasket. Tube end should be uniformally
indented on gasket with no signs of leak. If
signs of exhaust gas leakage are present,
replace gaskets and tighten flange nuts to
23 N-m (200 in. lbs.). If an intake plenum
leak persists, replace EGR tube and gaskets,
following installation instructions.
Verify correct hose connections and leak
check and confirm that all hoses are open.
If defective hoses are found, replace nose
harness.
(cl) Refer to Group 14, General Diagnosis "On
Board Diagnostics" to check solenoid.
(b)
(c)
NOTE: D O NOT ATTEMPT TO CLEAN BACK-PRESSURE EGR VALVE, REPLACE
ENTIRE VALVE/TRANSDUCER ASSEMBLY IF NECESSARY.
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