Ford VSG-411 Service Manual page 72

03A-8
Emission Control Svstem 03A-8
DIAGNOSIS AND TESTING (Continued)
EGR Valve Leakage Check
Perform this test if the engine stalls, idles roughly, or runs
poorly.
1.
Remove and cap the EGR valve vacuum hose. Start
the engine. If the engine idle quality improves
noticeably, double-check the vacuum hose routing
because the valve may have a vacuum supply at idle.
2.
If the enaine idle auatitv does not imDrove, remove
the EGR" valve froh the spacer. Blodk the' EGR
passages with a plate or install a known good EGR
valve. Start the engine. If the idle quality is still bad,
the problem is elsewhere. Reinstall the EGR valve. If
the idle quality improves noticeably, the EGR valve
has excessive leakage and should be replaced.
Testing for EGR Source Vacuum
Occasionally the EGR system may fail to operate because
the vacuum port on the carburetor is plugged, or because
of a vacuum leak. To test for source vacuum:
1. Remove the EGR supply vacuum hose from its
connection at the carburetor.
2.
Attach a vacuum gauge to the source.
3.
Start the engine and watch the gauge as you momen-
tarily accelerate to half throttle 3000 rpm maximum).
The vacuum should rise at off-idle, decrease at half
throttle, and go to zero at closed throttle.
If the source vacuum is okay, test the PVS and inspect
the hoses. If the source vacuum is not okay, check for an
obstruction in the carburetor or for a vacuum leak caused
by loose mounting.
CARBURETOR
EGR
HOSE
Testing the 2-Port PVS Valve
The Z-port PVS valve is okay if it blocks vacuum from the
EGR valve when the engine is cold and allows a vacuum
to get to the valve when the engine is hot.
WARNING: LET THE ENGINE COOL AND RELEASE
COOLING SYSTEM PRESSURE BEFORE REMOVING
THE VALVE, OR YOU COULD BE BURNED. IT ALSO
MAY BE NECESSARY TO DRAIN OUT SOME OF THE
COOLANT.
REMOVE BOTH HOSES
CONNECT VACUUM
GAUGE TO ONE PORT
AND REMOTE VACUUM
APPLY 10 INCHES
VACUUM TO VALVE
OPERATE ENGINE UNTIL
COOLANT WARMS ABOVE
VALVE SETTING
THIS GAUGE
1.
Remove both hoses from the PVS valve. 4. Run the engine until the coolant is warmer than the PVS
2. Connect a vacuum gauge to one port of the PVS
valve setting. PVS valves are color coded. This engine
valve and connect a vacuum pump to the other
has a black PVS valve that opens at 38°C (1 OOOF).
port.
5.
See if there is a vacuum reading on the gauge that is
3.
Apply IO inches of vacuum to the PVS valve.
connected directly to the PVS valve.
There should be a vacuum reading on the gauge. If there
is no vacuum, replace the PVS valve.