Acura NSX 1991 Manual page 275

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Intake Air Bypass (IAB) Control Valve Testing
CAUTION: Do not adjust the IAB control valve full-close
screw. It was preset at the factory.
1. Check the IAB control valve shaft for binding or
sticking.
2. Check the IAB control valve for smooth movement.
3. Check that of the IAB control valve is in close
contact with the stopper when the vacuum hose is
disconnected from the IAB control diaphragm.
4. Check that of the IAB control valve is in close
contact with the full-close screw when you apply
50.7 kPa (380 mmHg, 15.0 in.Hg) of vacuum to the
IAB control diaphragm.
If any fault is found, clean the linkage and shafts
with carburetor cleaner.
If the problem still exists after cleaning, disas-
semble the intake manifold and check the IAB
valve body assembly (see
Table of Contents
STOPPER
FULL-CLOSE
SCREW
section 9).