ignition ACURA NSX 1991 Service Repair Manual

5. Install the side engine mount, then tighten the bolts
in the numbered sequence as shown ( - ),

12 x
1.26
mm

73 N·m
(7.3 kg-m,
53 Ib-ft)

Replace.
12 x
1.25
mm

95 N·m
(9.5 kg-m,
69 Ib-ft)

SIDE ENGINE

MOUNT

6. Tighten the transmission mount mounting bolt.

MOUNTING BOLT
12 x
1.25
mm

95 N·m (9.5 kg-m, 69 Ib-ft)
7. Tighten the rear mount mounting bolt.
MOUNTING BOLT

12 x
1.25
mm

77 N·m (7.7 kg-m, 56 Ib-ft)
Replace.

Check that the spring clip on the end of each
driveshaft clicks into place.
CAUTION: Use new spring clips.
Bleed air from the cooling system (see page 10-5).
Bleed air from the brake lines {see section 19).
Check the clutch pedal free play (see section 12).

Adjust the clutch guide assemblies when disas-

sembling clutch (see section 12).

Check that the transmission shifts into gear

smoothly.

Adjust the alternator belt (see section 23).
Adjust the A/C compressor belt (see section 22).
Clean battery posts and cable terminals with
sandpaper, assemble, then apply grease to pre-
vent corrosion.
Inspect for fuel leakage (see section 11). After assembling the fuel line parts, turn on
the ignition switch (do not operate the starter) so that the fuel pump operates for approxi-
mately two seconds and the fuel line pressu-
rizes. Repeat this operation two or three times
and check for fuel leakage at any point in the

fuel line.

Check and adjust wheel alignment (see section 18).

Refill the engine with engine oil (see page 8-4 ('91-'92
Models), ('93-Model),or ('94-'96 Models).

Refill the transmission with oil/fluid (see section

13 or
14).ProCarManuals.com

Rocker Arms


Manual Inspection

1. Remove the ignition coil covers (see page 6-15 ('91-'93) or ('94-'96)
2. Remove the ignition coils (see page 6-15 ('91-'93)or ('94-'96).

3. Remove the cylinder head covers.

NOTE: Refer to pages 6-47 ('91-'93)
or ('94-'96) ,48 ('91-'93)

or ('94-'96) when installing the cylinder head cover.

4. Set the No. 1 piston at top dead center (TDC) (see

page 6-19 ('91-'93)
or ('94-'96).
5. Push the mid rocker arms on the No. 1 cylinder man-

ually.

6. Check that the mid rocker arms move independently
of the primary and secondary rocker arms.

MID ROCKER

ARM
SECONDARY

ROCKER ARM

PRIMARY

ROCKER ARM

7. Check the mid rocker arms of each cylinder at TDC. If a mid rocker arm does not move, remove the

mid, primary and secondary rocker arms as an

assembly and check that the pistons in the mid
and primary rocker arms move smoothly.
Replace the rocker arms as an assembly if there
is any abnormality. Rocker Arms


Inspection Using

Special Tools

CAUTION:
Before using the special tool, make sure that the air
pressure gauge on the air compressor indicates over
250 kPa (2.5 kg/cm2. 36 psi). Inspect the valve clearance before rocker arm inspec-

tion.

Cover the timing belt with a shop towel to prevent

getting oil on the belt.

Check the mid rocker arms of each cylinder at TDC.

1. Plug the relief hole with the special tool as shown.

Front cylinder head:

RELIEF HOLE

VTEC PLUG

07MAJ–PR7020A

VTEC INSPECTION HOLE

SEALING BOLT

Rear cylinder head:

RELIEF HOLE
VTEC PLUG

07MAJ–PR7020A

VTEC INSPECTION HOLE

SEALING BOLT
(cont'd)ProCarManuals.com

Timing Belt

Inspection

1. Remove the ignition coil covers and harness clamps.
2. Disconnect the connectors, then remove the ignition
coils.
3. Remove the cylinder head covers,
4. Inspect the timing belt for cracks and coolant or oil soaking.

NOTE:
Replace the belt if coolant or oil soaked.
Remove any oil or solvent that gets on the belt.

Inspect this area

for wear.

Rotate pulley and

Inspect belt.
Tension Adjustment

CAUTION:
Always adjust timing belt tension with the engine cold
Do not rotate the crankshaft when the adjusting bolt
is loose (the timing belt will skid over the teeth of
the rear intake caimshaft pulley).
Adjust the belt tension only when the belt has been
removed and reinstalled or replaced.

NOTE:
Tensioner is spring-loaded to apply proper tension to
the belt automatically after making the following ad-
justment. Inspect the timing belt before adjusting the belt
tension.
Always rotate the crankshaft clockwise. Rotating it
counterclockwise may result in improper adjustment
of the belt tension or cause the belt to jump a tooth
on the camshaft pulleys.
Install the timing beIt with the No. 1 piston at TDC
(see pages 6-18 ('91-'93) or ('94-'96),19 ('91-'93)
or ('94-'96) Remove the slack in the sequence of , and

by turning each camshaft pulley slightly.
Loosen the timing belt adjusting bolt 180° (the slack
at should be eliminated).

Then, tighten the timing belt adjusting bolt.

Verify that No. 1 piston is at TDC (see page 6-19).
Rotate the crankshaft clockwise nine teeth on the
camshaft pulley (The blue mark on the crankshaft pul- ley should line up with the pointer on lower cover).
Loosen
the
timing
belt
adjusting
bolt.

Retighten the adjusting bolt, torque to 43 N·m (4.3
kg-m, 31 Ib-fl).
Direction

of rotation

POINTER ON
LOWER COVER

ADJUSTING BOLT

43N·m (4.3 kg-m,

31 Ib-ft)
BLUE MARK
TDC MARK
ProCarManuals.com

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

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

Engine Coolant Refilling and Bleeding

CAUTION: When pouring engine coolant, be sure to

shut the relay box lid and not let coolant spill on the

electrical parts or the paint. If any coolant spills, rinse it

off immediately.

NOTE:

• Perform this maintenance when the engine is cool.

• Before replacing the coolant, turn the ignition ON,

slowly turn the climate control temperature knob to

90° and turn off the ignition. This will allow the

coolant in the heater to drain out with the rest of the

system.
1. Open the hood, the rear window and the engine

cover.

2. Remove the cover protecting the water pipes and

shift cables on the underside of the car.

3. Before removing the expansion tank cap, first

loosen the cap to lower pressure.

CAUTION: Do not remove the expansion tank cap

when engine is hot. The coolant is under pressure

and may blow out and scald you. Open the cap

slowly when the engine is cool.

4. Loosen the drain plug in the bottom of the radiator,

and drain the coolant.

5. Remove the two drain bolts from the water pipes,

and drain the coolant.

WASHERS

Replace.

DRAIN BOLTS

15 N-m (1.5 kg-m, 11 Ib-ft)
DRAIN HOLE
DRAIN PLUGProCarManuals.com

II. Engine Control Module (ECM) Reset Procedure

Either of the following actions, will reset the ECM.

• Using the OBD-II scan tool or Honda PGM Tester to clear the ECM's memory.

NOTE: See the OBD-II scan tool or Honda PGM Tester user's manuals for specific operating instructions.

• Turn the ignition switch OFF. Remove the CLOCK (7.5 A) fuse from the under-hood fuse/relay box for 10 seconds.

UNDER-HOOD

FUSE/RELAY BOX
CLOCK

(7.5 A) FUSE

III. Final Procedure (this procedure must be done after any troubleshooting)

1. Remove the SCS Service Connector if it is connected.

NOTE: If the SCS service connector is connected and there are no DTCs stored in the ECM, the MIL will stay on

when the ignition switch is turned on.

2. Do the ECM Reset Procedure.

3. Turn the ignition switch OFF.

4. Disconnect the OBD-II scan tool or Honda PGM Tester from the Data Link Connector,ProCarManuals.com

PGM-FI System

System Description

PGM-FI System

The PGM-FI system on this model is a sequential multiport fuel injection system.

Fuel Injector Timing and Duration

The ECM contains memories for the basic discharge durations at various engine speeds and manifold pressures. The

basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors

to obtain the final discharge duration.

Throttle Valve Control

The ECM controls the throttle valve control motor based on accelerator pedal position, TCS control unit and various sig-

nals. The ECM also controls the idle control function, cruise control function, and other functions with the throttle valve

control.

Ignition Timing Control

• The ECM contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing

is also adjusted for engine coolant temperature.

• A knock control system is also used. When detonation is detected by the knock sensor (KS), the ignition timing is

retarded.

Other Control Functions

1. Starting Control

When the engine is started, the ECM provides a rich mixture by increasing fuel injector duration.

2. Fuel Pump Control

• When the ignition switch is initially turned on, the ECM supplies ground to the PGM-FI main relay that supplies

current to the fuel pump for two seconds to pressurize the fuel system.

• When the engine is running, the ECM supplies ground to the PGM-FI main relay that supplies current to the fuel pump.

• When the engine is not running and the ignition is on, the ECM cuts ground to the PGM-FI main relay which cuts

current to the fuel pump.

• Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Valve Lift Electronic

Control System), intake air bypass control and discharge volume control of the fuel pump.ProCarManuals.com

Engine Control Module (ECM)

NOTE: If this symptom is intermittent, check for a loose No. 5 BACK-UP LIGHTS, ALTERNATOR,

TURN SIGNALS (15 A) fuse in the under-dash fuse/relay box, a poor connection at ECM terminal

A7, or an intermittent open in the BLU wire between the ECM (A7) and the gauge assembly.

Is the low oil pressure light on?

Try to start the engine.

Does the engine start?

Check for an open in the wire or

bulb:

1. Turn the ignition switch OFF.

2. Connect the ECM connector ter-

minal A7 to body ground with a

jumper wire.

3. Turn the ignition switch ON (II).

Is the MIL on?

Substitute a known-good ECM,

and recheck. If symptom/indica-

tion goes away, replace the origi-

nal
ECM.
— Repair short in the wire

between No. 5 BACK-UP

LIGHTS, ALTERNATOR, TURN

SIGNALS (15 A) fuse and

gauge assembly.

— Replace No. 5 BACK-UP

LIGHTS, ALTERNATOR, TURN

SIGNALS (15 A) fuse.

ECM CONNECTOR A (26P)

Check for an open in the wires

(PG line):

1. Turn the ignition switch ON (II).

2. Measure voltage between

body ground and ECM connec-

tor terminals A12 and A25 indi-

vidually.
WIRE SIDE OF FEMALE TERMINALS

Is there less than 1.0 V?
Repair open in the wire(s)

between ECM and G101 (located

at intake manifold) that had

more than 1.0V.

— Repair open in the wires

between ECM (A7) and gauge

assembly.

— Replace the MIL bulb.
WIRE SIDE OF FEMALE TERMINALS
ECM CONNECTOR A (26P)
Substitute a known-good ECM

and recheck. If symptom/indica-

tion goes away, replace the origi-

nal
ECM.
Turn the ignition switch ON (II).
The Malfunction Indicator Lamp

(MIL) never comes on (even for

two seconds) after ignition is

turned ON (II).ProCarManuals.com

Starter Switch Signal

This signals the ECM when the engine is cranking.

Inspection of Starter Switch Sig-

nal.
NOTE:

• M/T: Clutch pedal must be depressed.

• A/T: Transmission in position.

ECM CONNECTORS

Measure voltage between ECM

connector terminals C6 and A26

with the ignition switch in the

start position.

WIRE SIDE OF FEMALE TERMINALS

Is there battery voltage?

Is the fuse OK?
Repair short in the wire

between the ECM (C6) and

the No. 7 STARTER SIGNAL

(7.5 A) fuse or the PGM-FI

main relay.

Replace the No. 7 STARTER

SIGNAL (7.5 A) fuse.
Starter switch signal is OK.

Repair open in the wire between

the ECM
(C6)
and the No. 7

STARTER SIGNAL (7.5 A) fuse.
Inspect the No. 7 STARTER SIG-

NAL (7.5 A) fuse in the under-

dash fuse box.ProCarManuals.com