ACURA NSX 1991 Service Owners Manual

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

15. Loosen the idler pulley center nut and adjusting nut,

then remove the air conditioning (A/C) compressor
belt.

IDLER PULLEY
CENTER NUT

45 N·m
(4.5 kg-m,

33 lb-ft)

ADJUSTING

NUT

A/C COMPRESSOR

BELT

16. Remove the crankshaft pulley (see page 6-12 ('91-'93)
or ('94-'96)

17. Remove the rubber seal from the adjusting bolt,
then remove the middle covers and lower cover.

6 x 1.0 mm

12 N·m
(1.2 kg-m.

9 Ib-ft)
LOWER COVER RUBBER SEAL
6 x 1.0 mm
12 N·m
(1.2 kg-m,

9 lb-ft)

9 x
1.25
mm

22 N·m
(2.2 kg-m,

16 Ib ft)
IDLER PULLEY
ASSEMBLYCOLLAR
MIDDLE COVER
18. Loosen the adjusting boll 180
0
turn. Push the ten-

sioner to remove tension from the timing belt, then
re tighten the adjusting bolt.

ADJUSTING BOLT
Do not remove. When
adjusting, loosen

it
180°.

19. Remove the timing belt from the pulleys.ProCarManuals.com

Timing Belt

Installation

Install the timing belt in the reverse order of removal;

Only key points are described here.

NOTE: Clean the middle and lower covers before instal-

lation.

1. Set the timing belt drive pulley so that the No. 1 pis-

ton is at top dead center (TDC). Align the mark on

the teeth side of the timing belt drive pulley to the

pointer on the oil pump.

POINTER

MARK

KEY

TIMING BELT

DRIVE PULLEY

Clean.

2. Set the front camshaft pulleys so that the No. 1 pis-

ton is at TDC. Align the TDC marks on the front

exhaust camshaft pulley and front intake camshaft

pulley to the pointer on the back cover.

Pointer on the

back cover.

FRONT INTAKE

CAMSHAFT PULLEY
FRONT EXHAUST

CAMSHAFT PULLEY

TDC MARKS
3. Set the rear camshaft pulleys so that the No. 1 pis-

ton is at TDC. Align the TDC mark on the rear intake

camshaft pulley to the pointer on the back cover.

Align the rear exhaust camshaft pulley one half

tooth clockwise past TDC.

REAR EXHAUST

CAMSHAFT PULLEY
Pointer on the

back cover.
REAR INTAKE

CAMSHAFT PULLEY

TDC MARKS

4. Install the timing belt tightly in the sequence shown.

Timing belt drive pulley (crankshaft)

Adjusting pulley Front exhaust camshaft pulley

Front intake camshaft pulley Water pump

pulley Rear intake camshaft pulley Rear

exhaust camshaft pulley.

NOTE: Make sure the timing belt drive pulley and

camshaft pulleys are at TDC.

5. Tension the timing belt between the pulleys in the

sequence A to E as shown below.ProCarManuals.com

6. Adjust the timing belt (see page 6-14 ('91-'93) or ('94-'96))

7. Install the lower cover and middle covers.

8. Install the crankshaft pulley, then tighten the pulley

bolt (see page 6-12 ('91-'93) or ('94-'96))
9. Check the crankshaft pulley and the camshaft pul- leys at TDC.
NOTE: To check the camshaft, try to insert 5.0 mm
pin punches as shown when the camshaft is at TDC.

TDC MARK
(White paint)
TDC MARK

FRONT:
TDC MARKS

5.0 mm

PIN PUNCHES BACK COVER
MIDDLE COVER
REAR: TDC MARK

5.0 mm

PIN PUNCHES
TDC MARK
MIDDLE COVER

TDC MARKS
10. If a camshaft is not positioned at TDC, remove the

timing belt and adjust the positioning following the

procedure on page 6-18 ('91-'93) or ('94-'96) then reinstall

the timing belt.

11. After installation, adjust the tension of each belt.
See section 23 for alternator belt tension adjust-

ment.

See section 22 for A/C compressor belt tension
adjustment.ProCarManuals.com

CKP/CYP Sensor

Replacement

NOTE: Turn the crankshaft so fhat the No. 1 piston is at
top dead center (see page 6-19 ('91-'93) or ('94-'96))
1. Remove the timing belt (see page
6-15 ('91-'93) or ('94-'96)

2. Remove the front intake end exhaust camshaft
pulleys.
3. Remove the back cover.
4. Remove the CKP/CYP sensor from the front
cylinder head.
5. Install the CKP/CYP sensor in the reverse order of
removal.

Refer to page 6-18 ('91-'93) or ('94-'96) and 19 when

('91-'93) or ('94-'96) installing thetiming belt.

10 x
1.25
mm

70 N·m
(7.0 kg-m,

51 Ib-ft)

6 x 1.0 mm
12N·m II.2 kg-m,

9 Ib-ft) FRONT INTAKE
CAMSHAFT PULLEY

CKP/CYP

SENSOR

FRONT

CAMSHAFTS

TIMING
BELT

FRONT EXHAUST
CAMSHAFT PULLEY

10 x
1.25
mm

70 N·m
(7.0 kg-m,

61 Ib-ft)

BACK

COVER

MIDDLE COVER

6 x 1.0 mm
12N·m (1.2 kg-m.

9 Ib-ft)
LOWER COVERProCarManuals.com

Cylinder Head s
Illustrate d Inde x
CAUTION : T o avoi d damage , wai t unti l th e engin e coolan t temperatur e drop s belo w 100° F (38°C ) befor e removin g th e cylin -
de r head .
NOTE : Us e ne w O-ring s an d gasket s whe n reassembling .
Prio r t o reassembling , clea n al l th e part s i n solvent , dr y them , an d appl y lubrican t t o an y contac t parts .
6 x 1. 0 m m10N- m (1.0 kg-m ,7 Ib-ft )
CAMSHAF T HOLDE R
DOWE L PI N
O-RIN G
Replace . CAMSHAF
T HOLDE R
PLATE
6 x 1. 0 m m12N- m (1.2 kg-m ,9 Ib-ft ) CKP/CY
P SENSO R
6 x 1. 0 m m12N- m (1.2 kg-m ,9 Ib-ft )
RUBBE R SEAL S
Replac e whe n damage dor deteriorated .
BACK COVE R
8 x 1.2 5 mm22N- m (2. 2 kg-m , 1 6 Ib-ft )Apply oi l t o th e bol t threads .
FRONT INTAK ECAMSHAF T
RUBBER SEAL S
Replac e fo r oi l
leakage .
FRON T EXHAUS T
CAMSHAF T
DOWEL PI N
CAMSHAF T PULLE Y
OI
L SEA L
Replace .
DOWE
L PI N
10 x 1.2 5 mm70N- m (7. 0 kg-m ,51 Ib-ft )
ProCarManuals.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

INTAKE VALV E
SPRIN G OUTE R VALV
E KEEPER S
SPRIN G RETAINE R
INTAK E VALV E
SPRIN G INNE R
CYLINDE R HEA D BOL T
11 x 1. 5 m m78 N- m (7. 8 kg-m , 5 6 Ib-ft )Apply engin e oi l t oth e bol t threads .
CYLINDE R HEA D
GASKE T
Replace . CYLINDE
R HEA D BOLT S
11 x 1.5 m78N- m (7. 8 kg-m , 5 6 Ib-ft )
Appl y engin e oi l t o
the bol t threads .
VALVE SPRIN G SEA T
EXHAUS T VALV E
SPRIN G
SPRIN G RETAINE R
VALVE KEEPER S
VALVE SEA L
VALV E GUID E
LOS T MOTIO N
ASSEMBL Y
Test , 6-3 2
CYLINDE R HEA D
GASKE TReplace .
DOWEL PI N
OI L CONTRO L ORIFIC E
Remov e wit h 6 m m
bol t an d clean .
O-RING S
Replace . CYLINDE
R HEA D ORIFIC ERemove wit h 6m mbolt an d clean .
VALVE SEA L
VALV E GUID E
LOS T MOTIO N
ASSEMBL Y VALV
E SPRIN GSEAT
EXHAUS T VALV E
INTAK E VALVE
DOWEL PIN S
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