Honda Acura NSX 1991 Service Manual page 259

Description
To prevent erratic running when the engine is warming
up, it is necessary to raise the idle speed. The fast idle
air bypass valve is controlled by a thermowax plunger.
When the engine is cold, the engine coolant surroun-
ding the thermowax contracts the plunger, allowing ad-
ditional air to be bypassed into the intake manifold so
that the engine idles faster. When the engine reaches
operating temperature, the valve closes, reducing the
amount of air bypassing into the manifold.
AIR BYPASS VALVE
FAST'
IDLE
VALVE
Replace
WAX
Inspection
NOTE: The fast idle valve is factory adjusted; it should
not be disassembled.
1 . Start the engine.
2. Remove the cover of the fast idle valve.
3. Put your finger on the valve seat area and,make
that there is air flow with the engine cold (coolant
temperature below 30°C, d6'F) and idling.
l
If not, replace the fast idle valve and retest.
4. Warm up the engine (cooling fan comes on).
5. Check that the valve is completely closed. If not,
air suction can be felt in the valve seat area.
Replace the fast idle valve and recheck.
sure
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