(5) Replace the PCV valve and retest the system if
it does not operate as described in the preceding
tests. Do not attempt to clean the old PCV valve.
(6) If the paper is not held against the opening in
valve cover after new valve is installed, the PCV
valve hose may be restricted and must be replaced.
The passage in the intake manifold must also be
checked and cleaned.
(7) To clean the intake manifold fitting, turn a 1/4
inch drill (by hand) through the fitting to dislodge
any solid particles. Blow out the fitting with shop air.
If necessary, use a smaller drill to avoid removing
any metal from the fitting.
PCV VALVE/PCV SYSTEM TEST—4.7L V-8
ENGINE
(1) Disconnect PCV line/hose (Fig. 18) by discon-
necting rubber connecting hose at PCV valve fitting.
(2) Remove PCV valve at oil filler tube by rotating
PCV valve downward until locating tabs have been
freed at cam lock (Fig. 18). After tabs have cleared,
pull valve straight out from filler tube. To prevent
damage to PCV valve locating tabs, valve must
be pointed downward for removal. Do not force
valve from oil filler tube.
(3) After valve is removed, check condition of valve
o-ring (Fig. 18). Also, PCV valve should rattle when
shaken.
(4) Reconnect PCV valve to its connecting line/
hose.
(5) Start engine and bring to idle speed.
(6) If valve is not plugged, a hissing noise will be
heard as air passes through valve. Also, a strong vac-
uum should be felt with a finger placed at valve
inlet.
(7) If vacuum is not felt at valve inlet, check line/
hose for kinks or for obstruction. If necessary, clean
out intake manifold fitting at rear of manifold. Do
this by turning a 1/4 inch drill (by hand) through the
fitting to dislodge any solid particles. Blow out the
fitting with shop air. If necessary, use a smaller drill
to avoid removing any metal from the fitting.
(8) Do not attempt to clean the old PCV
valve.
(9) Return PCV valve back to oil filler tube by
placing valve locating tabs (Fig. 18) into cam lock.
Press PCV valve in and rotate valve upward. A slight
click will be felt when tabs have engaged cam lock.
Valve should be pointed towards rear of vehicle.
(10) Connect PCV line/hose and connecting rubber
hose to PCV valve.
(11) Disconnect rubber hose from fresh air fitting
at left side of air cleaner resonator box (Fig. 19).
Start engine and bring to idle speed. Hold a piece of
stiff paper (such as a parts tag) loosely over the
opening of the disconnected rubber hose.
(12) The paper should be drawn against the hose
opening with noticeable force. This will be after
allowing approximately one minute for crankcase
pressure to reduce.
(13) If vacuum is not present, disconnect each PCV
system hose at top of each breather (Fig. 19). Check
for obstructions or restrictions.
(14) If vacuum is still not present, remove each
PCV system breather (Fig. 19) from each cylinder
head. Check for obstructions or restrictions. If
Fig. 16 Vacuum Check at Valve Cover Opening
1 – STIFF PAPER PLACED OVER RUBBER GROMMET
2 – RUBBER GROMMET
3 – VALVE COVER
4 – FITTING REMOVED FROM VALVE COVER
5 – AIR TUBE
Fig. 17 Shake PCV Valve—Typical
1 – PCV VALVE GROMMET
2 – PCV VALVE
3 – PCV VALVE MUST RATTLE WHEN SHAKEN
25 - 30 EMISSION CONTROL SYSTEMS DN
DIAGNOSIS AND TESTING (Continued)
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