1991 ACURA NSX light

Idle Control System
Troubleshooting Flowchart Automatic Transaxle (A/T) Gear Position
Signal
This signals the ECM when the transmission is in Neutral or Park.
Inspection of A/T gear position

signal.

Turn the ignition switch ON.
Observe the A/T gear position in-
dicator and select each position
separately.

Does the indicator light properly?
Turn the ignition switch OFF.
Connect the test harness be-
tween the ECM and connector.
Disconnect "B" connector from

the engine wire harness only, not

the ECM (see page 11-37).

Turn the ignition switch ON.

Measure voltage between B7

( + ) terminal and A26 (-) ter-

minal.
Is there approx. 10V?
Turn the ignition switch OFF.
Reconnect "B" connector to the
engine wire harness.
Turn the ignition switch ON.
(To page 11-95) See A/T gear position switch in-
dicator inspection (see section
14).
Substitute a known-good ECM
and recheck. If prescribed voltage is now available, replace
the original ECM.ProCarManuals.com

Idle Control System
Idle Speed Setting
Inspection/Adjustment NOTE: (Canada) Pull the parking brake lever up.
Start the engine, then check that the head lights

are
off.
1. Start the engine and warm it up to normal operating temperature (the cooling fan comes on).
2. Connect a tachometer. Connect a tachometer to loop of ICM second-
ary, or...
TACHOMETER

ICM

Remove the rubber cap from the tachometer
connector and connect a tachometer.
TACHOMETER
TACHOMETER CONNECTOR
RUBBER

CAP
3. Disconnect the 2P connector from the IAC valve.
IAC VALVE
4. Start the engine with the accelerator pedal slightly depressed, then turn the headlights and rear defog-
ger ON. After the MIL comes on, stabilize the

engine speed at 1000 rpm, then slowly release the

pedal until the engine idles.

If the engine stalls, turn the idle adjusting screw
one turn counterclockwise and recheck.
5. Check idling with the headlights and rear defogger
on.

Idle speed should be:
M/T
A/T
550 ± 50 rpm
550 ± 50 rpm (in or range)
Adjust the idle speed, if necessary, by turning
the idle adjusting screw.
If the proper idle speed cannot be achieved,
clean the throttle body port with carburetor
cleaner.

IDLE ADJUSTING

SCREWProCarManuals.com

6. Turn the ignition switch OFF.

7. Reconnect the 2P connector on the IAC valve, then

remove CLOCK fuse in the under-hood fuse/relay

box for 10 seconds to reset ECM.

8. Restart and idle the engine with no-load conditions

in which the headlights, blower fan, rear defogger,

cooling fan, and air conditioner are not operating

for one minute, then check the idle speed.

Idle speed should be:

M/T

A/T
800
50 rpm

750
50 rpm

(in or range)ProCarManuals.com

Throttle Bod y
Descriptio n
The throttl e bod y i s o f th e single-barre l side-draf t type .
The lowe r portio n o f th e throttl e valv e i s heate d b y
engin e coolan t whic h is fe d fro m th e cylinde r head . Th e
idl e adjustin g scre w whic h increases/decrease s bypas s
ai r 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 .
A throttl e valv e dashpo t i s use d t o slo w th e throttl e
valv e a s i t approache s th e close d position .
THROTTL EVALVEDASHPO TCONTRO L THROTTL E
DIAPHRAG M STO P SCRE W
Inspectio n
CAUTION : D o no t adjus t th e throttl e sto p screw .
It i s prese t a t th e factory .
1. Star t th e engin e an d allo w i t t o reac h norma l
operatin g temperatur e (th e coolin g fa n come s on) .
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 .
3 . Allo w th e engin e t o idl e an d chec k tha t th e gaug e
indicate s n o vacuum .
IDLE ADJUSTIN GSCREW(Non-adjustable )
TPSENSO R
THROTTL EACTUATO R
THROTTLEVALVE
ACCELERATO RPEDALANGL ESENSO R
VACUU M PUMP/GAUG EA973X–041 –XXXX X
If ther e is vacuum , chec k th e throttl e cabl e (se e
pag e 11-130 ).
4 . Chec k tha t vacuu m is indicate d o n th e gaug e whe n
th e throttl e i s opene d slightl y fro m idle .
I f 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 it wit h carbureto r cleaner .
5. Sto p th e engin e an d chec k tha t th e throttl e cabl e
operate s smoothl y withou t bindin g o r sticking .
I f ther e ar e an y abnormalitie s in th e abov e steps ,
chec k for :
Excessiv e wea r o r pla y i n th e throttl e valv e
shaft .
Stick y o r bindin g throttl e leve r a t ful l clos e
position .
Clearanc e betwee n throttl e sto p scre w an d
throttl e leve r a t ful l clos e position .
(cont'd )
ProCarManuals.com

Emission Contro l Syste m
The emissio n contro l syste m include s a Thre e Wa y
Catalyti c Converter , Exhaus t Ga s Recirculatio n (EGR )
system , Positiv e Crankcas e Ventilatio n (PCV ) syste m
an d Evaporativ e Emissio n (EVAP ) contro l system .
Th e emissio n contro l syste m i s designe d t o mee t
federa l an d stat e emissio n standards .
Tailpipe Emissio n
1. Startin g th e engin e an d war m i t u p t o norma l
operatin g temperatur e (th e coolin g fa n come s on )
b y drivin g th e ca r o n th e road .
2 . Connec t a tachometer .
3 . Chec k idl e spee d an d adjus t th e idl e speed , i f
necessar y (se e pag e 11-102 ).
4 . War m up an d calibrat e th e C O mete r accordin g to 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 conditione r off .
C O mete r shoul d indicat e 0. 1 % maximum .
System Descriptio n
Do no t smok e durin g thi s procedure . Kee pany ope n flam e awa y fro m you r wor k area .
Inspectio n
ProCarManuals.com

Positive Crankcase Ventilation (PCV) System

Description

The Positive Crankcase Ventilation (PCV) system is

designed to prevent blow-by gas from escaping to the

atmosphere. The PCV valve contains a spring-loaded

plunger. When the engine starts, the plunger in the PCV

valve is lifted in proportion to intake manifold vacuum

and the blow-by gas is drawn directly into the intake

manifold.

PCV HOSE

BREATHER PIPE

FRONT OF

VEHICLE

BLOW-BY VAPOR

FRESH AIR

PCV VALVE

If there is no clicking sound, check the PCV

valve grommet for cracks or damage. If the

grommet is OK, replace the PCV valve and

recheck.
Gently pinch here
2. At idle, make sure there is a clicking sound from the

PCV valve when the hose between PCV valve and

intake manifold in lightly pinched with your fingers

or pliers.
BREATHER

PIPE
PCV VALVE PCV HOSE
Inspection

1. Check the PCV hoses and connections for leaks

and clogging.ProCarManuals.com

Transmission Assembly

Removal

CAUTION: Use fender covers to avoid damaging

painted surfaces.
1. Check and record the rear wheel alignment (see section 18).
2. Disconnect the battery negative (—), and positive (+) cables from the battery.
3. Drain transmission oil. Reinstall the drain plug with a new washer.
Corrosion resistant bolt/nut 4. Remove the strut bar.
5. Remove the air cleaner assembly.
6. Remove the connectors from the control box and remove the control box.
CAUTION: Do not remove the vacuum tubes from
the control box.
7. Remove the wire harness holder, jumper connector and transmission ground cable.
8. Disconnect the switch connectors, then remove the back-up light switch and neutral positionswitch.
9. Disconnect the starter motor cables, then remove the starter motor.
10. Remove the transmission mount.
11. Remove the two transmission housing bolts.
TRANSMISSION HOUSING BOLTS

BACK-UP

LIGHT SWITCH

CONNECTOR

WIRE HARNESS HOLDER

STARTER MOTOR

CABLES
NEUTRAL

POSITION
SWITCH

CONNECTOR

STARTER
MOTOR
TRANSMISSION

GROUND

CABLE

TRANSMISSION
MOUNT
MOUNTING

BOLTS
TRANSMISSION

HANGER
TRANSMISSION
MOUNTING BOLTS
JUMPER

CONNECTOR

VEHICLE SPEED

SENSOR (VSS)

CONNECTOR

CONTROL BOX

Make sure lifts are placed properly, and

hoist brackets are attached to correct position (see sec-

tion 1).ProCarManuals.com

BEARING OUTER RACE

75 mm THRUST SHIM

Selection.

CLAMP

BACK-UP LIGHT SWITCH
25 N.m (2·5 kg-m. 18 Ib-ft)
CLAMP
TRANSMISSION HANGER A
TRANSMISSION HANGER B

STAY

WASHER

Replace.

OIL FILLER PLUG
45 N .
m (4·5 kg-m. 33 Ib-ft)
42 x 63 x 12.5 mm OIL SEAL
Replace.

WASHER

Replace.

DRAIN PLUG
40 N·m (4.0 kg-m. 29 Ib-ft) 36 mm SEALING BOLT
35 N .
m (3.5 kg-m, 25 Ib-ft)

STRAINER COVER
O-RING
Replace.

STRAINER SET SPRING
OIL PUMP STRAINER 14 mm SEALING BOLT
33 N .
m (3.3 kg-m, 24 Ib-ft)
SPRING (L. 25 mm)

STEEL BALL (3/8 in)

16 mm SEALING BOLT

42 N .
m (4.2 kg-m. 30 Ib-ft)
SPRING (L. 25.1 mm)
16 mm SEALING BOLTS
42 N .
m (4.2 kg-m. 30 Ib-ft)
SPRING (L. 30 mm)

STEEL BALL (5/16 in)

SHIFT LEVER ASSEMBLY Removal, page 13-17

Installation, page 13-43

NEUTRAL POSITION SWITCH
25 N .
m (2.5 kg-m, 18 Ib-ft)
TRANSMISSION HOUSING
OIL GUIDE PLATE

82 mm THRUST SHIM
Selection, page 13-41ProCarManuals.com