Honda Civic 1998 Service Manual page 312

a
1 . After the engine starts, the IAC valve opens for a certain time, The amount of air is increased to raise the idle speed
about 150 - 300 rpm.
When the coolant temperature is low, the IAC valve is opened to obtain the proper tast idle speed. The amount of
bypassed air is thus controlled in relation to the engine coolant temperature.
IOLE SPEED
lrpml
176
80
Et{Gt1{E
COOLANT TEMPERATURE
( o F )
t o c )
L
1 .
When the idle speed is out of specification and the scan tool does not indicate Diagnostic Trouble Code {DTC} P0505
or P1508, check the following items:
. A d j u s t t h e i d l e s p e e d ( s e e p a g e 1 1 , 1 4 1 )
. S t a r t e r s w i t c h s i g n a l ( s e e p a g e l l - 1 3 0 I
. A i r c o n d i t i o n i n g s i g n a l ( s e e p a g e 1 1 - 1 3 1 )
. ALT FR signal (see page 11 133)
'
Brake switch signal {see page 1'l-134)
'
PSP switch signal (except Canada model) (see page 11-135)
. A/T gear position signal (see section '14, D16Y5 engine (CVT):
p a g e 1 l - 1 3 7 )
. Clutch switch signal (D16Y5 engine (M/T)) (see page 11-139)
.
Hoses and connections
. IAC valve and its mounting O-rings
lf the above items are normal. substitute a known-good IAC valve and readjust the idle speed (see page 11-141).
lf the idle speed still cannot be adlusted to specification (and the scan tool does not indicate DTC P0505 or P1508)
after IAC valve replacement, substilute a known-good ECM/PCM and recheck. lf symptom goes away, replace the
original ECM/PCM.
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