1991 ACURA NSX light

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

IAB CONTROL

SOLENOID

VALVE

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

IAB

CONTROL

DIAPHRAGM

IAB

CONTROL

VALVE
CLOSED: LOW ENGINE SPEEDProCarManuals.com

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
Inspectio n
Do no t smok e durin g thi s procedure . Kee p
an y ope n flam e awa y fro m you r wor k area .
1 . Star t th e engine . Hol d th e engin e a t 3,00 0 rp m wit h
no loa d (A/ T in position , M/ T in neutral ) unti l
the 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 11-128 ).
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 .
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Exhaust Ga s Recirculatio n (EGR ) Syste m
The EG R syste m is designe d t o reduc e oxide s o f nitroge n emission s (NOx ) b y recirculatin g exhaus t ga s throug h th e EG R
valv e an d th e intak e manifol d int o th e combustio n chambers . I t i s compose d o f th e EG R valve , EG R vacuu m contro l valve ,
EGR contro l solenoi d valve , EC M an d variou s sensors .
The EC M contain s memorie s fo r idea l EG R valv e lift s fo r varyin g operatin g conditions . Th e EG R valv e lif t senso r detect s
th e amoun t o f EG R valv e lif t an d send s th e informatio n t o th e ECM . Th e EC M the n compare s it wit h th e idea l EG R valv e lif t
whic h i s determine d b y signal s sen t fro m th e othe r sensors . I f ther e is an y differenc e betwee n th e two , th e EC M varie s cur -
ren t t o th e EG R contro l solenoi d valv e to regulat e vacuu m applie d t o th e EG R valve .
EGRVALV ELIFTSENSO R
INTAKEMANIFOL D
To No . 5 BACK-U P
LIGHT S ALTERNATO R
TUR N SIGNAL S
(1 5 A ) FUS E
EGRVACUU MCONTRO LVALVE
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Emission Control System
Positive Crankcas e Ventilatio n (PCV ) Syste m
Descriptio n
Th e Positiv e Crankcas e Ventilatio n (PCV ) syste m is
designe d t o preven t blow-b y ga s fro m escapin g t o th e
atmosphere . Th e PCV valve contain s a spring-loade d
plunger . Whe n th e engin e starts , th e plunge r i n th e PC V
valv e i s lifte d i n proportio n t o intak e manifol d vacuu m
an d th e blow-b y ga s i s draw n directl y int o th e intak e
manifold .
PCV HOS EINTAK E MANIFOL D
PCV VALV E
Inspectio n
1. Chec k th e PC V hose s an d connection s fo r leak s an d
clogging .
BREATHE RPIPE
PCV HOS E PC
V VALV E
2. A t idle , mak e sur e ther e i s a clickin g soun d fro m th e
PC V valv e whe n th e hos e betwee n PC V valv e an d
intak e manifol d i n lightl y pinche d wit h you r finger s
o r pliers .
Gently pinc h her e
If ther e i s n o clickin g sound , chec k th e PC V valv e
gromme t fo r crack s o r damage . I f th e gromme t i s
OK , replac e th e PC V valv e an d recheck .
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Evaporative Emission (EVAP) Controls

Description

The evaporative emission controls are designed to minimize the amount of fuel vapor escaping to the atmosphere. The

system consists of the following components:

A. Evaporative Emission (EVAP) Control Canister

An EVAP control canister is used for the temporary storage of fuel vapor until the fuel vapor can be purged from the

EVAP control canister into the engine and burned.

B. Vapor Purge Control System

EVAP control canister purging is accomplished by drawing fresh air through the EVAP control canister and into a port

on the throttle body. The purging vacuum is controlled by the EVAP purge control diaphragm valve and the EVAP

control solenoid valve.

EVAP PURGE CONTROL SOLENOID VALVE OFF AFTER

STARTING ENGINE

ENGINE COOLANT TEMPERATURE ABOVE 153°F (67°C)

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

FRESH

AIR
EVAP

PURGE CONTROL

DIAPHRAGM VALVE
EVAP PURGE

CONTROL

SOLENOID VALVE
EVAP PURGE

FLOW SWITCH
C. Fuel Tank Vapor Control System

When fuel vapor pressure in the fuel tank is higher than the set value of the EVAP two way valve, the valve opens and

regulates the flow of fuel vapor to the EVAP control canister.

EVAP

TWO WAY

VALVE
FUEL

FILL CAPProCarManuals.com

Transmission Assembl y
Removal
Make sur e lift s ar e place d properly , an d
hois t bracket s ar e attache d t o correc t position s (se e
sectio n 1 ).
CAUTION : Us e fende r cover s t o avoi d damagin g
painte d surfaces .
1 . Chec k an d recor d th e rea r whee l alignmen t (se e
sectio n 18 ).
2 . Disconnec t th e batter y negativ e (- ) an d positiv e (+ )
cable s fro m th e battery .
3 . Drai n transmissio n oil . Reinstal l th e drai n plu g wit h
a ne w washer .
Corrosio n resistan t bolt/nu t
4. Remov e th e stru t bar .
5 . Remov e th e ai r cleane r assembly .
6 . Remov e th e connector s fro m th e contro l box , an d
remov e th e contro l box .
CAUTION : D o no t remov e th e vacuu m tube s fro m
th e contro l box .
7 . Remov e th e wir e harnes s holder , jumpe r connecto r
an d transmissio n ground cable.
8 . Disconnec t th e back-u p ligh t switch , neutra l posi -
tio n switch , differentia l spee d sensor , an d vehicl e
speed senso r (VSS ) connectors .
9. Disconnec t th e starte r moto r cables , the n remov e
th e starte r motor .
10 . Remov e th e transmissio n mount .
11 . Remov e th e tw o transmissio n housin g bolts .
TRANSMISSIO N
HOUSIN G BOLT S
CONTROL BO X
BACK-U PLIGHT SWITC H
CONNECTO R
WIR E HARNES S HOLDE R
STARTER MOTOR
CABLES
NEUTRA L
POSITIO N
SWITCHCONNECTO R
DIFFERENTIA L
SPEE D SENSO R
VEHICL E SPEE D
SENSO R (VSS )
CONNECTO R
JUMPERCONNECTO R
TRANSMISSIO N
MOUNTING BOLT S
TRANSMISSIO NHANGER
STARTE RMOTOR MOUNTIN
G TRANSMISSIO N
BOLT S MOUN T
TRANSMISSIO
N
GROUN D
CABLE
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Transmission Housing

Removal

NOTE: Place the clutch housing on two pieces of wood

thick enough to keep the mainshaft from hitting the

workbench.

1. Remove the back-up light switch, neutral position

switch, differential speed sensor and vehicle speed

sensor (VSS).

VSS

(O-RING Replace.)
NEUTRAL

POSITION

SWITCH

DIFFERENTIAL

SPEED SENSOR

BACK-UP LIGHT SWITCH

2. Remove the sealing bolts, springs and steel balls.

3. Remove the transmission housing attaching bolts

in a crisscross pattern in several steps.

4. Remove the 36 mm sealing bolt.

SPRING

(L. 25 mm)

ATTACHING

BOLT
.14 mm SEALING BOLT

36 mm SEALING BOLT

STEEL BALL (3/8 in)

12 mm SEALING

BOLT

16 mm SEALING

BOLT COMP
5. Expand the snap ring on the countershaft ball bear-

ing, and remove it from the groove using a pair of

snap ring plier.

SNAP RING PLIER

SNAP RING

6. Separate the clutch housing from the transmission

housing.

7. Remove the thrust shim and oil guide plate from the

transmission housing.

THRUST SHIM

OIL GUIDE

PLATE

TRANSMISSION HOUSING
SPRING

(L.
24.2
mm)

STEEL

BALLS (5/16 in)ProCarManuals.com

17. Install new boot bands on the boots, then bend both

sets of locking tabs.

18. Lightly tap on the doubled-over portions to reduce

their height.

NOTE: Install the outboard joint in the knuckle

before installing the driveshaft into the differential

or intermediate shaft. Loosely install the spindle

nut this time.
19. Install the new set rings in the driveshaft groove

and intermediate shaft groove.

20. Apply a light film of grease around the set ring groove

on the inboard joint, then install a new set ring and

center it on the joint. The grease will keep the set

ring centered, making the installation of the joint

easier.

21. Install the inboard end of the driveshaft into dif-

ferential or intermediate shaft.

CAUTION:

• Always use a new set ring whenever the drive-

shaft is being installed.

• Make sure the left driveshaft locks in the dif-

ferential side gear groove, and the CV joint

subaxle bottoms in the differential.

• Insert the right driveshaft CV joint subaxle into

the intermediate shaft until the intermediate

shaft set ring locks in the groove in the right

driveshaft.

Apply light film of

grease before installing.

INBOARD JOINT

SET RING

Replace.
SET RING GROOVE

Left Driveshaft

inboard end
Right Driveshaft

inboard end

(Intermediate shaft side)
LOCKING TABSProCarManuals.com