ACURA NSX 1991 Service Repair Manual

Valve Clearance

Adjustment

Valves should be adjusted cold when the cylinder head

temperature is less than 100°F (38°C).

Adjustment is the same for both intake and exhaust

valves.

Adjust valve clearance at TDC of each cylinder.

Do not rotate the engine counterclockwise. The tim-

ing belt could jump a tooth on the camshaft pulleys.

EXHAUST

INTAKE

INTAKE

EXHAUST

TDC MARK (WHITE PAINT)

CRANKSHAFT PULLEY
POINTER ON

THE LOWER

COVER
TDC mark (white paint) on the crank pulley should

align with pointer on the timing lower cover, and

TDC grooves on the camshaft pulleys should align

with timing belt cover plates.

FRONT:

No.1 PISTON at TDC

REAR:
NOTE:

1. Remove the cylinder head covers.

FRONT:

REAR:
2. Rotate crankshaft and set No.1 piston at TDC.ProCarManuals.com

(cont'd)
LOCKNUT

7 x
0.75
mm

20 N
.
m
(2.0 kg-m.
14 Ib-ft)
LOCKNUT

7 x
0.75
mm

20 N .
m
(2.0 kg-m.
14 Ib-ft)
EXHAUST:
6. Tighten locknut and check clearance again. Repeat
adjustment if necessary.
INTAKE:
3. Manually inspect the rocker arms for independent
operation (page 6-52, 53)
4. Adjust valves on No.1 cylinder.
TAPPET ADJUSTER

07MAA–PR70110

TAPPET LOCKNUT
WRENCH

07MAA–PR70120

EXHAUST:
NOTE: Use a mirror to check if the special tool is

positioned on the locknut correctly.
Adjusting screws are on primary and secondary
rocker arms.

Intake: 0.15-0.19 mm (0.006-0.007 in)
Exhaust: 0.17-0.21 mm (0.007-0.008 in)

5. Loosen locknut and turn adjustment screw until feel-
er gauge slides back and forth with slight amount

of drag.

INTAKE:ProCarManuals.com

Valve Clearance

Adjustment (cont'd)

7. Rotate the crankshaft 120° clockwise (camshaft

pulley turns 60°). Check that the front intake cam-

shaft pulley is positioned as shown.

Repeat step 3 to step 6

Number 4 piston at TDC:

8. Rotate the crankshaft 120° clockwise (camshaft

pulley turns 60°). Check that the front intake cam-

shaft pulley is positioned as shown.

Repeat step 3 to step 6.

Number 2 piston at TDC:

9. Rotate the crankshaft 120° clockwise (camshaft

pulley turns 60°). Check that the front intake cam-

shaft pulley is positioned as shown.

Repeat step 3 to step 6.

Number 5 piston at TDC:
11. Rotate the crankshaft 120° clockwise (camshaft

pulley turns 60°). Check that the front intake cam-

shaft pulley is positioned as shown.

Repeat step 3 to step 6.

Number 6 piston at TDC:
10. Rotate the crankshaft 120° clockwise (camshaft

pulley turns 60°). Check that the front intake cam-

shaft pulley is positioned as shown.

Repeat step 3 to step 6.

Number 3 piston at TDC:ProCarManuals.com

Engine Oil
Inspection
1. Check engine oil with the engine off and the car parked on level ground.
2. Make certain that the oil level indicated on the dipstick is between the upper and lower marks.
3. If the level has dropped close to the lower mark, add oil until it reaches the upper mark.
CAUTION: Insert the dipstick carefully to avoid
bending it. Replacement
CAUTION: Remove the drain plug carefully while the
engine is hot, the hot oil may cause scalding.
1. Warm up the engine.
2. Drain the engine oil.

WASHER
Replace.

OIL PAN DRAIN PLUG

45 N .
m (4.5 kg-m, 33 Ib-ft)

3. Reinstall the drain plug with a new washer, and
refill with the recommended oil.

CAUTION: Do not overtighten the drain plug.
Requirement

Capacity

Change API Service Grade: Use "Energy
Conserving II" SG grade oil,
10 W–30 prefered

5.0

Every 7,500 miles (12,000 km)

NOTE: Oil filter should be replaced at each oil
change.
Engine Oil Viscosity for Outside Temperature Ranges.

(5.3
US qt, 4.4 Imp qt)

for change, including filter.

6.3

(6.7
US qt, 5.5 Imp qt)

for engine overhaul.ProCarManuals.com

Intake Manifold

Illustrated Index
NOTE: Use new O-ring, gaskets and self-locking nuts. INSTALL PIPE
6 x 1.0 mm

12 N .
m
(1.2 kg-m,
9 Ib-ft)

6 x
1.0
mm
12 N .
m
(1.2 kg-m,
9 Ib-ft)
IGNITION CONTROL
MODULE (ICM)

5 x 10 mm

6 N·m (0.6 kg-m, 4 Ib-ft)
INTAKE AIR TEMPERATURE (IAT) SENSOR

6 x 1.0 mm
12 N·m
(1.2 kg-m,
9 Ib-ft)
THROTTLE BODY

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)

6 x 1.0 mm
12 N ·
m
(1.2 kg-m,
9 Ib-ft)
GASKETS

Replace.
WASHER (10 pieces).
Replace.
EGR PIPE
GASKET
Replace.
GASKETS

Replace. INSULATOR
COVER PLATE
TOP COVER

6 x 1.0 mm
12 N·m (1.2 kg-m, 9 Ib-ft)

EXHAUST GAS
RECIRCUIATION (EGR)

PORT

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

GASKET
Replace. INTAKE MANIFOLD
Replace if cracked or
if mating surfaces are
damaged.
IDLE AIR CONTROL
(IAC) VALVE
O-RINGS
Replace.
O-RINGReplace.

8 x
1.25
mm

22 N·m (2.2 kg-m, 16 Ib-ft)

6 x 1.0 mm
12 N·m
(1.2 kg-m,
9 Ib-ft)
FAST IDLE THERMO VALVE
INTAKE AIR BYPASS (IAB)
VALVE BODY
INTAKE MANIFOLD
CHAMBER

8 x
1.25
mm

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

Exhaust Manifold
Illustrated Index
NOTE: Use new gaskets and self-locking nuts.
HEATEDOXYGEN SENSOR

45 N·m
(4.5 kg-m,
33 Ib-ft)Be careful not to damage.

8 x
1.25
mm

22 N·m
(2.2 kg-m, 16 Ib-ft)
6 x 1.0 mm

12 N·m
(1.2 kg-m,
9 Ib-ft)
EXHAUST MANIFOLD

COVERS

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

8 x
1.25
mm

34 N·m
(3.4 kg-m,
25 Ib-ft)
Apply oil to the
nut threads.

Replace.
REAR EXHAUST MANIFOLD

GASKET

Replace.
SELF-LOCKING

NUT

8 x
1.25
mm

34 N·m
(3.4 kg-m,

25 Ib-ft)
Apply oil to the
nut threads.
Replace.

EXHAUST MANIFOLD

COVER

HEATED OXYGEN SENSOR
45 N·m (4.5 kg-m, 33 Ib-ft)
Be careful not to damage.

GASKET
Replace.

6 x 10 mm
12 N·m
(1.2 kg-m,
9 Ib-ft)
FRONT EXHAUST MANIFOLD
8 x
1.25
mm

22 N·m
(2.2 kg-m,16 Ib-ft)ProCarManuals.com

Exhaust Pipe and Muffler

Illustrated Index
NOTE: Use new gaskets and self-locking nuts.

6 x 1.0 mm
10 N·m
(1.0 kg-m,
7 Ib-ft)
GASKET Replace.
REAR THREE WAY
CATALYTIC
CONVERTER

6 x 1.0 mm
10 N·m
(1.0 kg-m,
7 Ib-ft)
GASKET

Replace.
TO REAR EXHAUST MANIFOLD

GASKET
Replace.

EXHAUST PIPE
REAR
TO FRONT EXHAUST

MANIFOLD

GASKET
Replace.
SELF-LOCKING NUT
10 x
1.25
mm

55 N·m (5.5 kg-m, 40 Ib-ft)

Replace.

: CORROSION RESISTANT BOLT FRONT
EXHAUST PIPEMUFFLER
SELF-LOCKING NUT
10 x
1.5
mm

34 N·m (3.4 kg-m, 25 Ib-ft)

Replace.

6 x 1.0 mm
10 N·m (1.0 kg-m, 7 Ib-ft) FRONT THREE WAY CATALYTIC
CONVERTER
GASKET

Replace. SELF-LOCKING NUT

10 x
1.25
mm

34 N·m
(3.4 kg-m,
25 Ib-ft)
Replace.

ENGINE MOUNT

REAR BEAM
BRACKET
RUBBER MOUNT

GASKET

Replace.

SELF-LOCKING NUT
10 x
1.25
mm

34 N·m (3.4 kg-m, 25 Ib-ft)
Replace.

8 x
1.25
mm

22 N·m
(2.2 kg-m,
16 Ib-ft)ProCarManuals.com

Special Tools

Ref. No.
Tool Number

A973X-041 -XXXXX

KS-AHM-32-003

07LAJ-PT3010A
07MAJ-PR70100

07JAZ-001000A

07406-0040001
Page Reference

11-62,116,
131,135,137,
146,148,154
11-37,50,55

11-37
11-37

11-156,157

11-106,113

Description

Vacuum Pump/Gauge
Digital Multimeter

Test Harness
Test Harness Vacuum/Pressure Gauge 0—4 in. Hg
Fuel Pressure Gauge
Qty

1
1
1

1

1
1ProCarManuals.com

Component Locations

Index

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Troubleshooting, page 11 -66
INTAKE AIR TEMPERATURE (IAT) SENSOR
Troubleshooting, page 11-70
FUEL PUMP RESISTER

Troubleshooting, page 11-124

CRANKSHAFT POSITION/CYLINDER POSITION
(CKP/CYP) SENSOR

Troubleshooting, page 11-64

FUEL

INJECTOR

RESISTER
Testing,

page 11-112
FRONT HEATED OXYGEN SENSOR (HO2S)
Troubleshooting, page 11-48
REAR KNOCK SENSOR (KS)

Troubleshooting, page 11-80

FRONT KNOCK SENSOR (KS)

Troubleshooting, page 11-80

REAR HEATED OXYGEN SENSOR (HO2S)
Troubleshooting, page 11-48
IDLE AIR CONTROL (IAC) VALVE

Troubleshooting, page 11 -88

FAST IDLE THERMO VALVE

Inspection, page 11-101

NEUTRAL SWITCH (M/T)

Troubleshooting, page 11-96

SERVICE CHECK CONNECTOR (2P)
Self-diagnostic Procedures, page 11-34
ENGINE CONTROL MODULE (ECM)
Self-diagnostic Procedures, page 11-34
Troubleshooting, page 11-42
PGM-FI

MAIN RELAY

Relay Testing, page 11-120

Troubleshooting, page 11-122
THROTTLE POSITION (TP) SENSOR

Troubleshooting, page 11 -68
CONTROL BOX
page, 11-7
ACCELERATOR PEDAL
ANGLE SENSOR

Troubleshooting, section 19
EXHAUST GAS RECIRCULATION (EGR) VALVE

Troubleshooting, page 11-145
EXHAUST GAS RECIRCULATION (EGR)
VALVE LIFT SENSOR

Troubleshooting, page 11-145ProCarManuals.com

Component Locations

Index
FUEL TANK EVAPORATIVE EMISSION(EVAP) VALVE
EVAPORATIVE EMISSION (EVAP) TWO WAY VALVE

Testing, page 11-157
FUEL PUMP

Troubleshooting, page 11-116
Testing, page 11-119

Replacement, page 11-119
FUEL FEED PIPE
FUEL FILTERReplacement, page 11-114
FUEL PRESSURE REGULATOR
Testing, page 11-113

Replacement, page 11-114

FUEL RETURN PIPE
FUEL INJECTORS

Troubleshooting, page 11-107
Replacement, page 11-110
FUEL PUMP RELAY

Troubleshooting, page 11-116
FUEL RAIL
FUEL TANK
Replacement, page 11-126

FUEL

VAPOR HOSE
EVAPORATIVE EMISSION
(EVAP) CONTORL CANISTER

Troubleshooting, page 11-154

FUEL FILL CAPProCarManuals.com