1997 ACURA NSX Service Repair Manual

Throttle Bod y
Descriptio n
Th e throttl e bod y i s o f th e single-barre l side-draf t type .
Th e lowe r portio n o f th e throttl e valv e i s heate d b y
engine coolan t whic h i s fe d fro m th e cylinde r head . Th e
idl e adjustin g screw , whic h increases/decrease s bypas s
air , an d th e evaporativ e emissio n (EVAP ) contro l caniste r
por t ar e locate d o n th e to p o f th e throttl e body .
IDLE ADJUSTIN GSCREW
THROTTL E VALV E
CONTRO L MOTO R
TPSENSO R THROTTL
EVALVE
Inspectio n
CAUTION : D o no t adjus t th e throttl e sto p screw . I t i s
prese t a t th e factory .
1 . Star t th e engine . Hol d th e engine at 3,00 0 rp m wit h
no loa d (A/ T in o r position , M/ T i n neutral ) unti l
th e radiato r fa n come s on , the n le t i t idle .
2 . Disconnec t th e vacuu m hos e (t o th e EVA P contro l
canister ) fro m th e to p o f th e throttl e body ; connec t
a vacuu m gaug e t o th e throttl e body .
VACUU M PUMP/GAUGE , 0-3 0 in.H g
A973 X - 04 1 - XXXX X
3. Allo w th e engine to idle , an d chec k tha t th e gaug e
indicate s n o vacuum .
I f ther e i s vacuum , chec k th e throttl e cabl e (se e
pag e 11-150 ).
4 . Chec k tha t vacuu m is indicate d o n th e gaug e whe n
the throttl e is opene d slightl y fro m idle .
If th e gaug e indicate s n o vacuum , chec k th e throttl e
bod y port . I f th e throttl e bod y por t i s clogged , clea n
i t wit h carbureto r cleaner .
(cont'd)
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Intake Air System

Throttle Body (cont'd)

Disassembly

THROTTLE BODY

IDLE ADJUSTING

SCREW

O-RING

Replace.

INTAKE AIR DUCT
THROTTLE VALVE

CONTROL MOTOR
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Description

The Fuel Injection Air (FIA) Control system enables fresh air to be drawn through the throttle body and fuel injector port.

IDLE ADJUSTING

SCREW
FUEL INJECTOR

THROTTLE

BODY
AIR FLOW
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Intake Air System

Intake Air Bypass (IAB) Control System

Description

Satisfactory power performance is achieved by closing and opening the intake air bypass (IAB) control valves. High torque

at low engine speed is achieved when the valves are closed, whereas high power at high engine speed is achieved when

the valves are opened.

INTAKE AIR BYPASS (IAB) CONTROL

SOLENOID VALVE ON

ENGINE SPEED IS ABOVE 4,800 rpm

OPEN: HIGH ENGINE SPEED

CLOSED: LOW ENGINE SPEED

IAB CONTROL

SOLENOID

VALVE

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

IAB

CONTROL

DIAPHRAGM

•IAB

CONTROL

VALVE
IAB

CHECK

VALVE

IAB

VACUUM

TANK
VARIOUS

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Troubleshooting
Inspection o f IA B Contro l System .
Chec k fo r vacuu m at idle :
1 . Star t th e engin e an d allo w it
to idle .2. Remov e th e No . 3 vacuu mhose fro m th e IA B contro ldiaphrag m an d connec t a vac -
uu m gaug e t o th e hose . VACUU
M PUMP/GAUGE , 0-3 0 in.H g
A97 3 - 04 1 - XXXX X
I s ther e vacuum ? Chec
k fo r vacuu m at IA B vacuu m
tank:Remov e No . 3 vacuu m hos e fro m
th e IA B vacuu m tank , the n chec k
fo r vacuu m a t th e IA B vacuu m
tank.
IAB CONTRO LDIAPHRAG M
Is ther e vacuum ?
Chec k fo r a n ope n in th e circuit :
1 . Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e 6 P connecto r
fro m th e contro l box .
3. Tur n th e ignitio n switc h O N(II).4. Measur e voltag e betwee n th e
contro l bo x connecto r termi -
nal s No . 3 an d No . 6 .
I s ther e batter y voltage ? Replac
e th e IA B contro l solenoi d
valve.
Check fo r a n ope n i n th e wir e
(IG 1 line) :
Measur e voltag e betwee n th e
contro l bo x connecto r termina l
No . 3 an d bod y ground .
(T o pag e 11-156 )
(cont'd)(To pag e 11-156 ) Repai
r th e blockag e o r vacuu m
lea k betwee n th e IA B vacuu m
tan k an d th e intak e manifold .
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Intake Ai r Syste m
Intake Ai r Bypas s (IAB ) Contro l Syste m (cont'd )
(From pag e 11-155 )
Chec k fo r vacuu m at 5,00 0 rpm :
1 . Rais e engin e spee d t o abov e
5,00 0 rpm .
2 . Chec k fo r vacuu m a t th e vac -
uu m hose .
I s ther e vacuum ?
IA B contro l syste m is OK . I
s ther e batter y voltage ?
Chec k fo r a n ope n i n th e wir e
(IABC S line) :
1 . Sto p th e engin e an d tur n th e
ignitio n switc h ON .2. Connec t EC M connecto r ter -minal s A2 0 t o A2 6 wit h ajumpe r wire .
Doe s th e solenoi d valv e clic k
whe n th e jumpe r i s connected ?
Substitut e a known-goo d EC M
an d rechec k (se e pag e 11-3 9 fo r
immobilize r information) . I f symp -
tom/indicatio n goe s away , replac e
th e origina l ECM .
I s ther e vacuum ?
Chec k fo r a shor t i n th e wir e
(IABC S line) :
1 . Tur n th e ignitio n switc h OFF .
2. Disconnec t th e EC M connec -tor A (26P ) fro m th e ECM .
3 . Chec k fo r continuit y betwee n
th e contro l bo x connecto r ter -
mina l No . 6 an d bod y ground .
I s ther e continuit y t o ground ?
Substitut e a known-goo d EC M
an d rechec k (se e pag e 11-3 9 fo r
immobilize r information) . I f symp -
to m goe s away , replac e th e origi -
nal ECM .
Repai r ope n i n th e wir e betwee n
th e contro l bo x 6 P connecto r an d
No . 5 BACK-U P LIGHT S ALTER -
NATO R TUR N SIGNAL S (I S A )
fus e in th e under-das h fus e box .
Repai r ope n i n th e wir e betwee n
EC M (A20 ) an d contro l bo x 6 P
connector .
Replac e th e IA B contro l solenoi d
valve.
Repai r shor t t o groun d a t th ewir e betwee n EC M (A20 ) an dcontro l bo x 6 P connector .
(Fro
m pag e 11-155 )
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Intake Ai r Bypas s (IAB ) Contro l Valv e Testin g
CAUTION : D o no t adjus t th e IA B contro l valv e full-clos e
screw . I t wa s prese t a t th e factory .
1 . Chec k th e IA B contro l valv e shaf t fo r bindin g o r
sticking .
2 . Chec k th e IA B contro l valv e fo r smoot h movement .
3. Chec k tha t o f th e IA B contro l valv e i s i n clos e
contac t wit h th e sto p whe n th e vacuu m hos e i s dis -
connecte d fro m th e IA B contro l diaphragm .
4. Chec k tha t o f th e IA B contro l valv e i s i n clos e
contac t wit h th e full-clos e scre w whe n yo u appl y
50. 7 kP a (38 0 mmHg , 15. 0 in.Hg ) o f vacuu m to th e
IA B contro l diaphragm .
FULL-CLOS E
SCRE W
If an y faul t i s found , clea n th e linkag e an d shaft s
wit h carbureto r cleaner .
I f th e proble m stil l exist s afte r cleaning , disassem -
bl e th e intak e manifol d an d chec k th e IA B valv e
bod y assembl y (se e sectio n 9 ).
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Emission Contro l Syste m
System Descriptio n
The emissio n contro l syste m include s tw o Thre e Wa y
Catalyti c Converter s (TWCs) , Exhaus t Ga s Recirculatio n
(EGR ) system , Positiv e Crankcas e Ventilatio n (PCV ) sys -
te m an d Evaporativ e Emissio n (EVAP ) Contro l system .
Th e emissio n contro l syste m is designe d t o mee t federa l
an d stat e emissio n standards .
Tailpipe Emissio n
1. Star t th e engine . Hol d th e engine at 3,00 0 rp m wit h
no loa d (A/ T in o r position , M/ T in neutral ) unti l
th e radiato r fa n come s on , the n le t i t idle .
2 . Connec t a tachometer .
3 . Chec k an d adjus t th e idl e speed , i f necessar y (se e
pag e 11-129 ).
4 . War m u p an d calibrat e th e C O mete r accordin g t o
th e mete r manufacturer' s instructions .
5 . Chec k idl e C O wit h th e headlights , heate r blower ,
rea r windo w defogger , coolin g fan , an d ai r condi -
tione r off .
NOTE : (Canada ) Pul l th e parkin g brak e leve r up .
Star t th e engine , the n chec k tha t th e headlight s ar e
off.
CO mete r shoul d indicat e 0.1 % maximum .
Inspection
any ope n flam e awa y fro m you r wor k area .
D
o no t smok e durin g thi s procedure . Kee p
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