engine ACURA NSX 1991 Service Owner's Manual

Removal

NOTE:
Before removing the belt, turn the crankshaft pulley
so the No. 8 piston is at top dead center (TDC) (see
page 6-19 ('91-'93) or ('94-'96)

Inspect the water pump after removing the timing
belt (see page 10-11).

If it is to be reused, mark the direction of rotation on

the belt.
1. Disconnect the battery negative terminal first, then the positive terminal,
2. Remove the right rear wheel/tire.
3. Remove the engine oil cooler base assembly- NOTE: Do not disconnect the hoses.

O-RING

Replace.

8 x
1.25
mm

22 N·m
(2.2 kg-m,
16 Ib-ft)

8 x
1.25
mm

22 N·m
(2.2 kg-m,

16 Ib-ft)

Replace.

4. Remove the strut brace (see page 5-3 ('91-'93) or ('94-'96)

5. Remove the intake manifold plate and top cover (see

page 6-25 ('91-'93) or ('94-'96)

4. Remove the ignition coil covers, the injector cover
and the wire harness covers.
5. Remove the ignition coils and the connectors.
NOTE:
There are front and rear ignition coils and covers.
They can be identified by the mark FF (front) orRR (rear) printed on them.
When installing front and rear ignition coil covers,
attach a rubber seal to the intake side.

6 x 1.0 mm

12 N·m
(1.2 kg-m,

9 Ib-ft)
IGNITION COIL

COVER

6 x 1.0 mm

10 N·m
(1.0 kg-m,

7 Ib-ft)

HARNESS

COVERS

6 x 1.0 mm
12 N·m
(1.2 kg-m,

9 Ib-ft)

CONNECTOR

IGNITION COIL

6. Remove the expansion tank.
NOTE: Do not disconnect water hoses.

6 x 1.0 mm
10 N·m (1.0 kg-m, 7 Ib-ft)

EXPANSION TANK

(cont'd)ProCarManuals.com

Timing Belt

Removal (cont'd)

7. Remove the breather hose and the air cleaner hous-
in
g
(see page 6-25 ('91-'93) or ('94-'96) )

8. Disconnect the alternator connector and the termi-

nal.

9. Remove the cover, adjusting bolt, the mounting bolt and mounting nut, then remove the alternator belt
and the alternator.

COVER

6 x 1.0 mm

12 N·m
(1,2 kg-m,

9 Ib-ft)

MOUNTING BOLT
10 x 1.25 mm

45 N·m
(4.5 kg-m,

33 Ib-ft)

ADJUSTING

BOLT

MOUNTING NUT
10 x
1.25
mm

45 N·m
(4.5 kg-m,

33 Ib-ft)
ALTERNATOR

BELT

10. Remove the cylinder head covers.

Refer to page 6-47 ('91-'93) or ('94-'96) when installing.

11. Remove the two bolts from the side engine mount
near the alternator bracket. Pivot the mounting bracket

into the housing of the body.

12 x 1.25 mm

73 N·m (7.3 kg-m, 53 Ib-ft)

Replace.

12 x
1.25
mm

95 N·tn (9,5 kg-m,
69 Ib-ft)
CORROSION RESISTANT BOLT

12. Remove the transmission mount (see page 5-10 ('91-'93)
or ('94-'96) transmission mount

13. Install a brace under the engine, then tilt the engine
approximately 5 using a jack.

NOTE: Make sure to place a cushion between the

oil pan and the jack.

14. Remove the alternator bracket stiffener and dipstic
pipe.

ALTERNATOR BRACKET
STIFFENER

8 x
1.25
mm
22N·m

(2.2 kg-m,
16 lb-ft!

10 x
1.25
mm

45 N·m
(4.5 kg-m,

33 Ib-ft!
6 x 1.0 mm

12N·m (1.2 kg-m, 9 Ib-ft)
DIPSTICK PIPProCarManuals.com

Cylinder Heads

Illustrated Index (cont'd)
CAUTION:
To
avoid
damage,
wait
until
the
engine
coolant
temperature
drops
below
100°F
(39-C]
before
removing
the
cylin-

der head.

NOTE: Use new O-rings and gaskets when reassembling.

Prior to reassembling, clean all the parts in solvent, dry them, and apply lubricant to any contact parts.

REAR VARIABLE VALVE TIMING
AND VALVE LIFT ELECTRONIC CONTROL
SYSTEM (VTEC) SOLENOID VALVE

Troubleshooting, page 6-3 ('91-'93) or ('94-'96)

EXHAUST GAS
RECIRCULATI0N (EGR) VALVE

6 x 1 .0 mm
12 N·m
(1.2 kg-m.
9 Ib-ft)
8 x
1.25
mm

22 N·m
(2.2 kg-m,
16 Ib-ft)
ENGINE COOLANT
TEMPERATURE (ECT) SENSOR
18 N·m (1.8 kg-m, 13 Ib-ft)

8 x
1.25
mm
22 N·m (2.2 kg-m. 16 lb-ft)
FRONT VTEC SOLENOID VALVE

Troubleshooting. page 6-3

SEALING BOLTS

60 N·m
(6.0 kg-m,

43 lb-ft)

OIL PRESSURE

GAUSE SENDING
UNIT (section 23)

ROCKER

SHAFTS
WASHERS
Replace.

8 x
1.25
mm

22 N·m
(2.2 kg-m,16 Ib-ft)
DOWEL PIN

0-RING

Replace.

ECT SWITCH

28 N·m
12.8 kg-m.

20 lb-ft

O-RING

Replace.

O-RING

Replace.

ROCKER ARM ASSEMBLY[PRIMARY. MID, SECONDARY]

Inspection, page 6-32 ('91-'93) or ('94-'96)

ROCKER SHAFT

OIL CONTROL
ORIFICE

Remove with 5 mm

boit and clean.

FILTER
Replace.

GASKET

Replace.

O-RING

Replace.ProCarManuals.com

Cylinder Heads

Removal

Engine removal is not required for this procedure. Make sure jacks and safety stands are
placed properly and hoist brackets ere attached to cor- rect positions on the engine.
CAUTION: Use a fender cover (special tool) to avoid damaging
painted surfaces. Unplug the wiring connectors carefully while holding
the connector portion to avoid damage.
To avoid damaging the cylinder heads, wait until the
engine coolant temperature drops below 100°F
(38°C) before loosening the retaining bolts. Do not open the engine cover when the roof panel is
stored (NSX-T open top).
NOTE:
Unspecified items are common.

Mark all wiring and hoses to avoid misconnection.
Also, be sure that they do not contact other wiring or

hoses or interfere with other parts.

Inspect the timing belt before removing the cylinder

head.

Turn the crankshaft pulley SO that the No. 1 piston is at top dead center (see page 6-19 ('91-'93) or ('94-'96)).
1. Disconnect the negative terminal from the battery.
2. Remove the expansion tank cap. Use care when removing the expan-
sion tank cap to avoid scalding by engine coolant
or steam.
3. Raise the car, then remove the right rear wheel/tire.
4. Drain the engine coolant (see page 10-5 ). 5. Remove the engine under guard, then remove the
front exhaust pipe A.

GASKETS
Replace.

FRONT EXHAUST

PIPE A

SELF-LOCKING NUT

10 x
1.25
mm

55 N·m (5.5 kg-m, 40 Ib-ft)
Replace.
SELF- LOCKING NUT

8 x
1.25
mm

22 N·m (2.2 kg-m. 16 Ib-ft)

Replace.

6. Remove the rear exhaust pipe A.

SELF- LOCKING NUT

8 x
1.25
mm
22 N·m (2.2 kg-m, 16 Ib-ft)

Replace.

REAR

EXHAUST

PIPE A

SELF-LOCKING NUT
10 x
1.25
mm

55 N·m (5.5 kg-m.

40 Ib-ft)

Replace.
GASKETS

Replace.

7. Remove the engine oil cooler base assembly (see
page 6-15 ('91-'93) or ('94-'96).

8. Lower the car.
9. Remove the strut brace (see page 5-3 ).ProCarManuals.com

10. Remove the engine cover stay from the strut brace,
then set the engine cover stay between the engine
cover and rear hatch latch (NSX-T open top),
CAUTION: Use a shop tower to avoid damaging

painted surfaces.

SHOP

TOWEL

11. Relieve fuel pressure by loosening the service bolt on the fuel filter about one turn (see section 11).
Do not smok* while working on fuel
system; Keep open flame or spark away from work

area. Drain fue1 only into an approved container.

12. Remove the fuel feed pipe and fuel return hose (see page 5-5 ('91-'93) or ('94-'96).

13. Remove the evaporative emission (EVAP) control
canister hose and brake booster vacuum hose (see
page 5-5 ('91-'93) or ('94-'96).
14. Disconnect the breather pipe and vacuum hose, then remove the air cleaner housing.

6 x 1.0 mm

10 N·m (1.0 kg-m, 7 lb-ftl

AIR CLEANER
HOUSING

BREATHER

PIPE

: CORROSION RESISTANT BOLT
15. Remove the Hoses, then remove the expansion tank
(see page 5-5 ('91-'93) or ('94-'96).
16. Removel the radiator hoses and heater hose (see
page 5-6 ('91-'93) or ('94-'96).

17. Disconnect the two connectors, then remove the
control box (see page 5-6 ('91-'93) or ('94-'96).

18. Remove the intake manifold plate and top cover.

INTAKE MANIFOLD

PLATE
6 x
1.0mm

12 N·m (12kg-m,

9 lb-ft)

TOP COVER

19. Remove the fuel injector covers.
6 x 1.0 mm
12 N·m (1-2 kg-m, 9 lb-ft)

FUEL INJECTOR

COVER

(cont'd)

ENGINE

COVER

STAYProCarManuals.com

24. Remove the engine wire harness connectors and
wire harness clamps from the cylinder head and
intake manifold, Six injector connectors
Intake air temperature (IAT) sensor connector
CKP/CYP sensor connector
Heated oxygen sensor (HO2S) connectors

Ignition control module (ICM) connectors

Engine coolant temperature (ECT) sensor connec-

tor

ECT gauge sending unit connector
ECT switch connector
Exhaust gas recirculation (EGR) valve lift sensor

connector

Throttle position sensor connector Engine oil pressure gauge sending unit connector
Knock sensor connector
VTEC solenoid valve connectors
VTEC pressure switch connectors
Engine oil pressure switch connector
Alternator connector

Alternator terminal

Throttle body 6P connector

25. Remove the ignition coils and connector.

26. Remove the EGR pipe and intake manifold assem- bly.

8 x 1.25mm

22 N·m (2.2 kg-m, 16 Ib-ft)

6 x 1.0 mm
12 N·m
(1.2 kg-m,

9 lb-ft)

GASKETS

Replace. INTAKE
MANIFOLD
ASSEMBLY

GASKET
Replace.
27. Loosen the adjusting nut and idler pulley center nut,
then remove the air conditioning compressor belt

(see page 6-17('91-'93) or ('94-'96)).

28. Remove the cover, adjusting bolt, mounting bolt and mounting nut, then remove the alternator belt
and alternator.

COVER

MOUNTING BOLT
10 x
1.25
mm

45 N·m (4.5 kg·m,

33 Ib-ft)

MOUNTING NUT
10 x
1.25
mm

45 N·m (4.5 kg·m.

33 Ib·ft)
ALTERNATOR

BELT

29. Disconnect the knock sensor connector, then remove
the wire holder.

6 x 1.0 mm
12N·m (1.2 kg-m, 9 Ib-ft)

KNOCK SENSOR
WIRE HOLDER
(cont'd)

6 x 1.0 mm

12 N·m (1.2 kg-m, 9 Ib-ft)

ADJUSTING

BOLTProCarManuals.com

Camshafts

Installation

5. Apply liquid gasket to the head mating surfaces of

the No. 1 and the No. 4 camshaft holders.

- Apply liquid gasket to the shaded areas.

6. Install the camshaft holders.

NOTE:

• "F" or "R" marks are stamped on the camshaft

holders.

• The arrows must be pointing to the timing belt

side.

• Set two dowel pins in each camshaft holder.

FRONT:

No. 4 No. 3 No. 2 No. 1

CAMSHAFT CAMSHAFT CAMSHAFT CAMSHAFT

HOLDER HOLDER HOLDER HOLDER

REAR:

No. 4 No. 3 No. 2 No. 1

CAMSHAFT CAMSHAFT CAMSHAFT CAMSHAFT

HOLDER HOLDER HOLDER HOLDER
7. Install the camshaft holder plates.

8. Tighten each bolt two turns at a time in the sequence

shown below to insure that the rockers do not bind

on the valves.

NOTE: Apply clean engine oil to 8 mm bolt threads.

Specified torque:

8 mm x 1.25 mm bolts:

22 N-m (2.2 kg-m, 16 Ib-ft)

6 mm x 1.0 mm bolts:

10 N-m (1.0 kg-m, 7 Ib-ft)

CAMSHAFT HOLDER BOLT TORQUE SEQUENCE

FRONT:ProCarManuals.com

Engine Bloc k
Illustrate d Inde x
Lubricat e al l interna l part s wit h engin e oi l durin g reassembly .
NOTE:
• Appl y liqui d gaske t t o th e matin g surface s o f th e
left sid e cove r an d oi l pum p cas e befor e install -
ing them .
• Us e liqui d gasket , par t No . 08718-0001 .
If th e botto m of th e oi l pa n is deformed , i t shoul d
be repaire d o r th e oi l pa n shoul d b e replace d re -
tain prope r clearanc e betwee n th e scree n an d
the bottom .
COVER
DRIVE PLAT E (A/T )
Chec k fo r cracks .
SPECIA L WASHE R
12 x 1. 0 m m75 N- m (7. 5 kg-m , 5 4 Ib-ft )
Torqu e sequence , pag e 7- 6
12 x 1. 0 m m105 N- m (10. 5 kg-m . 7 6 Ib-ft )
Torqu e sequence , pag e 7- 6
6 x 1. 0 m m14 N- m (1. 4 kg-m , 1 0 Ib-ft )
OIL PA N• D o no t defor mthe bottom .• Refe r t o pag e 8-1 0whe n installing .
OIL PA N GASKE TReplace
6 x 1. 0 m m12 N- m (1. 2 kg-m , 9 Ib-ft )
O-RIN G
Replace .
CRANKSHAF TOIL SEA LInstallation , pag e 8- 9Replace .
CRANKSHAF T OI L SEA L
Installation , pag e 7-1 8
Replace .
SPECIAL BOL T6 x 1. 0 m m12 N- m (1. 2 kg-m ,9 Ib-ft )Replace .
OIL PAS S
PIPE/JOIN T
LEFTSIDE COVE R
Appl y liqui d gaske t
t o matin g surface . DOWE
L PIN S
OI L PUM P
Overhaul , pag e 8- 7
Removal/Inspection ,
pag e 8- 8
Appl y liqui d gaske t
t o matin g surface . SPECIA
L BOLT S
8 x 1.2 5 mm22 N- m (2. 2 kg- n16 Ib-ft )Replace .
SPECIAL BOLT S6 x 1. 0 m m12 N- m (1. 2 kg-m , 9 Ib-ft )Replace .
DOWEL PIN S
O-RING SReplace .
OIL SCREE N
FLYWHEE L (M/T )
Runout , sectio n 1 2
BAFFL E PLAT E
6 x 1. 0 m m12 N- m (1. 2 kg-m ,9 Ib-ft )
COVE R
ProCarManuals.com

Engine Bloc k
Illustrated Index
Lubricat e al l interna l part s wit h engin e oi l durin g reassembly .
MAIN BEARIN GCAP BRIDG E
10 x 1.2 5 mm50 N- m (5. 0 kg-m , 3 6 Ib-ft )
Appl y engin e oi l t o th e
bol t thread s an d th e washers .
MAI
N BEARIN G
CAP
CRANKSHAF TEnd play , pag e 7- 6
Runout , Taper , an d
Out-of-Round , pag e 7-1 1
Installation , pag e 7-1 8 to 7-2 1
THRUS T WASHER S
Replacement , pag e 7- 6
Groove d side s fac e outward .
NOTE : Thrus t washe r thicknes s
i s fixe d an d mus t no t b e change d
by grindin g o r shimming .
11 x 1. 5 m m66 N- m(6.6 kg-m , 4 8 Ib-ft )
Appl y engin e oi l t o th e bol t
threads and th e washers .
NOTE : Afte r torquin g
eac h cap , tur n crankshaf t
t o chec k fo r binding .
9 x 1.2 5 mm40 N- m (4. 0 kg-m , 2 9 Ib-ft )
Appl y engin e oi l t o th e
bol t thread s
DOWE L PI N
MAI N BEARING S
Radia l clearance , pag e 7- 7
Selection , pag e 7- 8
NOTE : Ne w mai n bearing s
mus t b e selecte d b y matchin g
cran k an d bloc k identificatio n
markings .
6 x 1. 0 m m12 N- m (1. 2 kg-m ,9 Ib-ft )
DOWE L PI N
OI
L BREATHIN GCOVER
O-RINGReplace .
ProCarManuals.com

Flywheel an d Driv e Plat e
Replacemen t
Manual Transmission :
Remove th e eigh t flywhee l bolts , the n separat e th e
flywhee l fro m th e crankshaf t flange . Afte r installation ,
tighten th e bolt s i n th e sequenc e shown .
RING GEA R HOLDE R07LAB -PV0010 0 o r
0792 4-PD2000 3
RING GEA R HOLDE R07LAB - PV00100 or
0792 4-PD2000 3
ENGINEBLOCK
RING GEA RInspec t rin g gea rteeth fo r wea r an ddamage .
12 x 1. 0 m m105 N- m(10. 5 kg-m , 7 6 Ib-ft )
Automati c Transmission :
Remov e th e eigh t driv e plat e bolts , the n separat e th e
driv e plat e fro m th e crankshaf t flange . Afte r installa -
tion, tighte n th e bolt s i n th e sequenc e shown .
12 x 1. 0 m m75 N- m(7.5 kg-m , 5 4 Ib-ft )
Connectin g Rod s an d
Crankshaf t
End Pla y
Connectin g Ro d En d Play :
Standar d (New) : 0.15—0.3 0 m m
(0.006-0.01 2 in )
Servic e Limit : 0.4 0 m m (0.01 6 in )
CONNECTIN G RO D CRANKSHAF T
• I f out-of-tolerance , instal l a ne w connectin g rod .
• I f stil l out-of-tolerance , replac e th e crankshaf t
(se e page s 7-9 , 7-1 0 an d 7-1 8 to 7-21 ).
Pus h th e crankshaf t firml y awa y fro m th e dia l indicator ,
an d zer o th e dia l agains t th e en d o f th e crankshaft . The n
pul l th e crankshaf t firml y bac k towar d th e indicator ; dia l
readin g shoul d no t excee d servic e limit .
SCREWDRIVE R
Crankshaft En d Play :
Standar d (New) :
0.10-0.3 5 mm
(0.004-0.01 4 in )
Servic e Limit : 0.4 5 m m (0.01 8 in )
• I f en d pla y i s excessive , inspec t th e thrus t
washer s an d thrus t surfac e o n th e crankshaft .
Replac e part s a s necessary .
NOTE : Thrus t washe r thicknes s i s fixe d an d mus t
no t b e change d eithe r b y grindin g o r shimming .
Thrus t washer s ar e installe d wit h groove d sid e fac -
in g outward .
ProCarManuals.com