1991 ACURA NSX torque

9. Install the CKP/CYP sensor on the front cylinder

head.

CKP/CYP SENSOR

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

10. Install the front and rear timing cover plates.

RUBBER SEALS

REAR COVER

PLATE

6x 1.0 mm
12 N.m
(1.2 kg-m.
9 Ib-ft)

RUBBER SEAL

FRONT COVER

PLATE
RUBBER SEALS
11. Insert the dowel pins in the camshaft pulley.
12. Install the camshaft pulleys then tighten the retain-
ing bolts to the torque specified.
NOTE: To set the camshafts at TDC, align the
camshaft holes with the camshaft holder pipe holes
and insert 5.0 mm pin punches as shown.

CAMSHAFT PULLEYS
5.0 mm

PIN PUNCHES

RETAINING BOLTS
10 x
1.25
mm

70 N.m (7.0 kg-m, 51 Ib-ft)

13. Install the timing belt (page 6-25, 26).

14. Adjust the valve clearance (page 6-54).
15. Inspect the rocker arms (pages 6-52, 53).
16. After installation, check that hoses and connectors
are installed correctly.

Prior to installing the cylinder head cover, apply
a thin layer of liquid gasket to the mating surface of the cylinder head cover and rubber seals to
prevent the rubber seal from falling off.

After installation, fill the engine with oil up to the

specified level, run the engine for more than 3
minutes, then check for oil leakage.

NOTE:ProCarManuals.com

3. Fuel Cut-off Control

During deceleration with the throttle valve closed, current to the fuel injectors is cut off to improve fuel economy

at speeds over 1,500 rpm.

Fuel cut-off action also takes place when engine speed exceeds, 8,300 rpm, regardless of the position of the

throttle valve, to protect the engine from over-revving.

4. A/C Compressor Clutch Relay

When the ECM receives a demand for cooling from the air conditioning system, it delays the compressor from being

energized, and enriches the mixture to assure smooth translation to the A/C mode.

5. Evaporative Emission (EVAP) Purge Control Solenoid Valve

When the engine coolant temperature is below 1 58 °F (70°C) the ECM supplies a ground to the EVAP purge control

solenoid valve which cuts vacuum to the EVAP purge control diaphragm valve.

6. Intake Air Bypass (IAB) Control Solenoid Valve

When the engine speed is below 4,800 rpm, the IAB control solenoid valve is activated by a signal from the ECM.

Intake air then flows through the smaller chamber, and hight torque is delivered. To increase air flow at engine speeds

higher than 4,800 rpm, the solenoid valve is deactivated by the ECM, and the intake air flows through the larger

chamber.

7. Exhaust Gas Recirculation (EGR) Control Solenoid Valve

When the EGR is required for control of oxides of nitrogen (NOx) emissions, the ECM supplies ground to the EGR

control solenoid valve which supplies regulated vacuum to the EGR valve.

ECM fail-safe/back-up Functions

1. Fail-Safe Function

When an abnormality occurs in a signal from a sensor, the ECM ignores that signal and assumes a pre-programmed

valve for that sensor that allows the engine to continue to run.

2. Back-up Function

When an abnormality occurs in the ECM itself, the fuel injectors are controlled by a back-up circuit independent of

the system in order to permit minimal driving.

3. Self-diagnosis Function [Malfunction Indicator Lamp (MIL)]

When an abnormality occurs in a signal from a sensor, the ECM lights the MIL and stores the diagnostic trouble code

in erasable memory. When the ignition is initially turned in, the ECM supplies ground for the MIL for two seconds

to check the MIL bulb condition.ProCarManuals.com

15. Tighten the transmission housing attaching bolts in
a criss-cross pattern in several steps shown below.

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

16. Install the 36 mm sealing bolt.
NOTE: Apply liquid gasket (P/N 08718–0001) to

the flange.
17. Install the steel balls, springs, and sealing bolts. NOTE: Apply liquid gasket (P/N 08718–0001) to
the threads, but don't plug the hole with liquid
gasket.

14 x 1.0 mm SEALING BOLT

33 N .
m (3.3 kg-m. 24 Ib-ft)

STEEL BALL
(3/8
in)

SPRING (L. 25 mm)

36 mm SEALING BOLT
35 N.
m (3.5 kg-m, 25 Ib-ft)
SPRING
(L.
25.1
mm)

SPRING
(L. 30 mm)

16 x 1.0 mm

SEALING BOLTS

42 N .
m

(4.2 kg-m,

30 Ib-ft)

STEEL BALLS

(5/16
in)

SPRING
(L. 30 mm)
18. Install the back-up light switch and neutral position

switch.

NOTE: Apply liquid gasket (P/N 08718–0001) to
the threads.
19. Install the vehicle speed sensor (VSS).

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

VSS
(O-RING Replace.)
8 x
1.25
mm

24 N .
m (2.4 kg-m, 17 Ib-ft)
NEUTRAL POSITION

SWITCH

25 N.
m
(2.5 kg-m,

18 Ib-ft)
BACK-UP LIGHT SWITCH
25 N .
m (2.5 kg-m,18 Ib-ft)

8x1.25 mm

24 N .
m (2.4 kg-m, 17 Ib-ft)

8 x
1.25
mm

26 N
.
m
(2.6 kg-m,

19 Ib-ft)ProCarManuals.com

Description

The automatic transmission is a combination of a 3-element torque converter and a triple-shaft electronically controlled

automatic transmission which provides 4 speeds forward and 1 in reverse. The entire unit is positioned in line with the

engine.

TORQUE CONVERTER, GEARS AND CLUTCHES

The torque converter consists of a pump, turbine and stator, assembled in a single unit.

They are connected to the engine crankshaft so they turn together as a unit as the engine turns.

Around the outside of the torque converter is a ring gear which meshes with the starter pinion when the engine is being

started. The entire torque converter assembly serves as a flywheel while transmitting power to the transmission mainshaft.

The transmission has three parallel shafts, the mainshaft, the countershaft, and the secondary shaft. The mainshaft is

in line with the engine crankshaft.

The mainshaft includes the clutches for 1st, and 4th, and gears for 3rd, 4th, Reverse and 1st (3rd gear is integral with

the mainshaft, while reverse gear is integral with 4th gear).

The countershaft includes the clutches for 1st-Hold and 3rd, and gears for 2nd, 3rd, 4th, Reverse and 1st.

The secondary shaft includes the 2nd clutch and gears for 2nd and 3rd.

The 4th and reverse gears can be locked to the countershaft at its center, providing 4th gear or Reverse, depending on

which way the selector is moved.

The gears on the mainshaft and secondary shaft are in constant mesh with those on the countershaft.

When certain combinations of gears in the transmission are engaged by clutches, power is transmitted from the main-

shaft to the countershaft to provide , , , and

ELECTRONIC CONTROL

The electronic control system consists of the Transmission Control Module (TCM), sensors, a linear solenoid and 4

solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions.

The TCM is located on the insulator center bulkhead, behind the driver's seat.

HYDRAULIC CONTROL

The valve bodies include the main valve body, secondary valve body, servo body, regulator valve body, throttle valve

body, lock-up valve body and the 2nd accumulator body.

They are bolted to the torque converter housing as an assembly.

The main valve body contains the manual valve, 1-2 shift valve, 2-3 shift valve, 3-4 shift valve, relief valve, one-way

relief valve and oil pump gears.

The secondary valve body contains the 3-2 kick-down valve, CPC (clutch pressure control) valve, 2nd orifice control

valve, 3rd orifice control valve, modulator valve, 4th exhaust valve, servo control valve, 2nd exhaust valve and 4-3 kick-

down valve.

The servo body contains the accumulator pistons and servo valve. The throttle valve body includes the throttle valve B

which is bolted onto the servo body.

The regulator valve body contains the pressure regulator valve, lock-up control valve and cooler relief valve. Fluid from

the regulator passes through the manual valve to the various control valves.

The lock-up valve body contains the lock-up timing B valve and lock-up shift valve. The 2nd accumulator body contains

the accumulator pistons and limited slip differential (LSD) relief valve.

The torque converter check valve is located in the torque converter housing, under the main valve body.

The 1st, 1st-hold, 3rd and 4th clutches receive oil from their respective feed pipes.

SHIFT CONTROL MECHANISM

Input from various sensors located throughout the car determines which shift control solenoid valve the TCM will ac-

tivate. Activating a shift control solenoid valve changes modulator pressure, causing a shift valve to move. This

pressurizes a line to one of the clutches, engaging that clutch and its corresponding gear.

LOCK-UP MECHANISM

In position and position in 2nd, 3rd and 4th, pressurized fluid is drained from the back of the torque converter

through an oil passage, causing the lock-up piston to be held, against the torque converter cover. As this takes place, the

mainshaft rotates at the same speed as the engine crankshaft. Together with hydraulic control, the TCM optimizes the

timing of the lock-up mechaism.

The lock-up valves control the range of lock-up according to lock-up control solenoid valves A and B, and throttle valve B.

When lock-up control solenoid valves A and B activate, modulator pressure changes. The lock-up control solenoid valves

A and B are mounted on the torque converter housing, and are controlled by the TCM.

(cont'd)ProCarManuals.com

LOCK-UP CONTROL

SOLENOID VALVE

ASSEMBLY
TORQUE CONVERTER

ATF COOLER

4TH CLUTCH

1ST CLUTCH

1ST-HOLD CLUTCH

2ND CLUTCH
3RD CLUTCH

DIFFERENTIAL ASSEMBLY

(LIMITED SLIP DIFFERENTIAL)

(cont'd)ProCarManuals.com

Description

Clutches (cont'd)

Lock-up Clutch

1. Operation (clutch on)

With the lock-up clutch on, the oil in the chamber between the converter cover and lock-up piston is discharged, and the

converter oil exerts pressure through the piston against the converter cover. As a result, the converter turbine is locked on the

converter cover firmly. The effect is to bypass the converter, thereby placing the car in direct drive.

The power flows by way of:

2. Operation (clutch off)

With the lock-up clutch off, the oil flows in the reverse of CLUTCH ON. As a result, the lock-up piston is moved away from the

converter cover; that is, the torque converter lock-up is released.

Engine

To oil cooler

INLET
To oil cooler

INLET

OUTLET
TORQUE CONVERTER

COVER COMP
LOCK-UP PISTON

DAMPER SPRING

Engine

Drive plate

Torque converter cover

Lock-up piston

Damper spring

Turbine

Mainshaft

Drive plate

Torque converter cover

Pump

Turbine

MainshaftProCarManuals.com

Power Flow

MAINSHAFT REVERSE GEAR
MAINSHAFT 1ST GEAR

1ST CLUTCH

1ST-HOLD CLUTCH

ONE-WAY CLUTCH COUNTERSHAFT 1ST GEAR PARKING GEAR
COUNTERSHAFT REVERSE GEAR COUNTERSHAFT 4TH GEAR
2ND CLUTCH
SECONDARY SHAFT 2ND GEAR SECONDARY SHAFT 3RD GEAR FINAL DRIVEN GEAR
(cont'd)

FINAL DRIVE GEAR
TORQUE CONVERTER
3RD CLUTCH
COUNTERSHAFT
3RD CLUTCH COUNTERSHAFT
2ND GEAR
4TH CLUTCH

MAINSHAFT

3RD GEAR

MAINSHAFT

4TH GEAR

O: Operates, x : Doesn't operate.

Although the 1st clutch engages, driving power is not transmitted as the one-way clutch slips.ProCarManuals.com

Description

Power Flow (cont'd)

Position

At position, hydraulic pressure is applied to the 1st clutch and to the 1st-hold clutch.

The power flow when accelerating is as follows;

1. Hydraulic pressure is applied to the 1st clutch on the mainshaft and power is transmitted via the 1st clutch to the

mainshaft 1st gear.

2. Power transmitted to the mainshaft 1st gear is conveyed via the countershaft 1st gear to the one-way clutch on

the inside of the countershaft 1st gear. The one-way clutch is used to drive the countershaft.

3. Power is transmitted to the final drive gear and drives the final driven gear.

Hydraulic pressure is applied to the 1st-hold clutch but the countershaft is rotated by the one-way clutch.

The power flow when decelerating is as follows;

1. Rolling resistance from the road surface through the rear wheels to the final drive gear, then to the countershaft

1st gear via the Ist-hold clutch which is applied during deceleration.

2. The one-way clutch becomes free at this time because of the countershaft rotates in reverse at the time of accelerating.

3. The counterforce conveyed to the countershaft 1st gear turns the mainshaft 1st gear. At this time, since hydraulic

pressure is also applied to the 1 st clutch, counterforce is also transmitted to the mainshaft. As a result, engine braking

can be obtained with 1st gear.

1ST CLUTCH

MAINSHAFT 1ST GEAR

MAINSHAFT
TORQUE CONVERTER

COUNTERSHAFT

FINAL DRIVEN GEAR
1ST-HOLD CLUTCH

COUNTERSHAFT 1ST GEAR

ONE-WAY CLUTCH

FINAL DRIVE GEARProCarManuals.com