1991 ACURA NSX fuel

Outline

Description

This engine is a 2,977 cm3 (181.6 cu-in) DOHC mid-ship unit having 6 cylinders of 90° —V configuration; it is water cool-

ed and equipped with a center plug type pent roof combustion chamber. It is specified for unleaded fuel and uses a

PGM-FI system: The PGM-FI system on this model is a sequential multiport fuel injection system.
PGM-FI system. This engine incorporates a new mechanism called Honda Variable Valve Timing and Valve Lift Elec-

tronic Control System (VTEC). This mechanism, the world's first, allows the timing and lift of the intake and exhaust

valves to be changed simultaneously. The engine also includes a new electronically-controlled intake manifold system

that can change the volume of the intake chamber.ProCarManuals.com

This engine has the following new features.

Type

Displacement
Bore x Stroke
Compression Ratio
Cam, Valve Mechanism
Valve Train
Fuel Supply System Water-cooled V6—90° Cross Flow
2,977 cm3(181.6cu-in)

90 x 78 mm
(3.54
x
3.07
in)
10.2
Dual Overhead Camshafts, VTEC Belt Driven
Sequential Multiport Fuel Injection (SFI)VTEC; High output and a broad power band is achieved through control of low-speed and high-speed valve operation
by the Engine Control Module (ECM).
(Two knock sensors are used to detect octane level of the fuel.)
Titanium connecting rods ; Accomodate high rotation speed and high output. Titanium material of light weight and
high strength is used for the connecting rods.
(Strength is at the same level as iron.)
(Weight is about 30% lighter than iron.)
New mechanism to the intake system; Increased low and middle speed torque and higher output can be achieved by
switching the chamber volume of the intake manifold according to engine speed. This is electronically-controlled.
Cooling system for the mid-ship engine:
Radiator located in front compartment (An aluminum alloy radiator and pipes made of aluminum alloy)
Engine room cooling fan
Expansion tank
The cylinder block is highly rigid with deep water jackets. In order to achieve lighter weight, magnesium is used for the following parts: Cylinder head coverIntake manifold cover
Intake manifold chamber
Major SpecificationsProCarManuals.com

Engine Removal/Installation

(cont'd)

10. Disconnect the resistor connector and fan motor connector, then remove the engine room fan
assembly.
ENGINE ROOM

FAN
ENGINE ROOM
FAN CONNECTOR
GROMMET
11. Remove the rear trim panels behind the
passenger's seat, then disconnect four connectors
from Engine Control Module (ECM) and five con- nectors from floor wire harness.
ENGINE WIRE
HARNESS CONNECTORS
ECM

PASSENGER'S

SEAT

FLOOR WIRE HARNESS
ENGINE WIRE

HARNESS

FUEL PUMP RESISTOR
CONNECTORGROUND

CABLE

6x1.0
mm

10 N.m (1.0 kg-m, 7 Ib-ft)
CORROSION RESISTANT BOLT
6 x 1.0 mm

10 N.m d.Okg.m, 7 Ib-ft)ProCarManuals.com

12. Remove the intake manifold plate and the top
cover.
13. Remove the throttle cable by loosening the locknut, then slip the cable end out of the throttle bracketand accelerator linkage.

INTAKE MANIFOLD
TOP COVER
6 x 1.0 mm

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

PLATE

ADJUSTING NUT

LOCKNUT
CABLE END

14. Relieve fuel pressure by slowly loosening the ser-
vice bolt on the fuel filter about one turn (see sec-

tion 11 ).

1 5. Remove the fuel feed pipe.
16. Remove the fuel return hose from the pressure con- trol valve.

6 x 1.0 mm

22 N .
m (2.2 kg-m. 16 Ib-ft) 12 N .
m (1.2 kg-m, 9 Ib-ft)
FUEL FEED
PIPE
WASHERS

Replace.

FUEL RETURN
HOSE

17. Disconnect two hoses, then remove the expansion tank.

6 x 1.0 mm
10 N .
m (1.0 kg-m, 7 Ib-ft)
EXPANSION TANK
WATER HOSES
(cont'd)

Do not smoke while working on the
fuel system. Keep open flame away from work
area. Drain fuel only into an approved container.
CAUTION:
THROTTLE CABLE

NOTE:

Take care not to bend the cable when removingit. Always replace a kinked cable with a new
one.
Adjust the throttle cable when installing (see
section 11).
Before disconnecting any fuel line, relieve the
fuel pressure as described above.
Place a shop towel over the fuel filter to prevent
pressurized fuel from spraying over the engine.ProCarManuals.com

Engine Removal/Installation

(cont'd)

Torque the engine mounting bolts in sequenceshown below.
CAUTION: Failure to tighten the bolts in the proper

sequence can cause excessive noise and vibration

and reduce bushing life; check that the bushings

are not twisted or offset.
Bleed air from the cooling system (see section 10)
Bleed air from the brake lines (see section 19)
Adjust the throttle cable tension.
Check the clutch pedal free play.
Adjust the clutch guide assemblies when
disassembling clutch (see section 12). Check that the transmission shifts into gear
smoothly (M/T see section 13, A/T see section 14).
Adjust the alternator belt (see section 23).
Adjust the A/C belt (see section 22).
Clean battery posts and cable terminals with sand-
paper, assemble, then apply grease to prevent

corrosion.

Inspect for fuel leakage:
• After assembling fuel line parts, turn on the igni- tion switch (do not operate the starter) so that
the fuel pump operates for approximately two seconds and the fuel line pressurizes. Repeat
this operation two or three times and check whether any fuel leakage has occurred at any
point in the fuel line.
Check and adjust wheel alignment.

10 x
1.25
mm

60 N .
m (6.0 kg-m, 43 Ib-ft)
MOUNTING BOLT SPECIAL BOLT

12 x
1.25
mm

77 N .
m
(7.7 kg-m,
56 Ib-ft)

Replace.
10 x
1.25
mm

60 N .
m
(6.0 kg-m
43 Ib-ft) 73 N.m (7.3 kg-m, 53 Ib-ft)

12 x
1.25
mm

95 N .
m
(9.5 kg-m,
69 Ib-ft)

RUBBER CAP

(M/T only)
SIDE MOUNT
: CORROSION RESISTANT
BOLT/NUT

12 x
1.25
mm

105 N .
m (10.5 kg-m, 76 Ib-ft)

10 x
1.25
mm

60 N .
m (6.0 kg-m, 43 Ib-ft) MOUNTING BOLT FRONT MOUNT
TRANSMISSION
MOUNT (A/T)

12 x
1.25
mm

95 N .
m
(9.5 kg-m,
69 Ib-ft)
SEAT STOPPER
TRANSMISSION
MOUNT (A/T)

REAR MOUNT
SPECIAL NUT
12 x
1.25
mm

77 N .
m
(7.7 kg-m,
56 Ib-ft)

Replace.
M/T:

A/T:

After the engine is in place:ProCarManuals.com

14. Relieve fuel pressure (see section 11).
Do not smoke while working on fuel
system; keep open flame or spark away from work
area. Drain fuel only into an approved container.
1 5. Disconnect the fuel feed pipe and the return hose
(page 5-21).

16. Remove the ignition coil covers, the wire harness covers, the ignition coils and the connectors (page
6-23).
17. Remove the water hoses, then remove the expan- sion tank (page 5-21).
18. Remove the breather hose, and the air cleaner housing (page 5-22).
19. Remove the brake booster hose, the evaporative emission (EVAP) control canister hose and other
hoses from the intake manifold and throttle body
(page 5-22).
20. Remove the emission control box (page 5-23). Do not disconnect emission hose.Disconnect the three connectors before
removing.
21. Remove the connector, the terminal and the alternator.
22. Disconnect the following engine wire harness con- nectors, then remove the harness clamps from thecylinder head and the intake manifold.
Front cylinder head:

Crankshaft position (CKP)/cylinder position
(CYP) sensor connector
Air conditioning (A/C) compressor magnetic clutch connector
Heated oxygen sensor (H02S) connector
Ground cable terminals Three injector connectors (cylinders No. 4, 5

and 6)

Intake air temperature (IAT) sensor connector
Ignition control module (ICM) connector
Condenser connector

Engine oil pressure gauge sending unit

connector

VTEC solenoid valve connector
VTEC pressure switch connector
Engine coolant temperature (ECT) sensor

connector
ECT sending unit connector
Accelerator pedal opening sensor connector

(throttle body)

Radiator fan control sensor connector
Rear cylinder head: Engine oil pressure switch connector (oil cooler

base)

Heated oxygen sensor connector
Three injector connectors (cylinders No. 1, 2

and 3)
Idle air control (IAC) valve connector
Knock sensor connector
Throttle actuator motor connector

Throttle position sensor connector

VTEC solenoid valve connectorVTEC pressure switch connector
ICM connector

Ground terminal

ICM CONNECTORS THROTTLE ACTUATOR

MOTOR CONNECTOR

THROTTLE POSITION
SENSOR CONNECTOR
ACCELERATOR PEDAL OPENING
SENSOR CONNECTORProCarManuals.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