engine ACURA NSX 1991 Service Repair Manual
[x] Cancel search | Manufacturer: ACURA, Model Year: 1991, Model line: NSX, Model: ACURA NSX 1991Pages: 1640, PDF Size: 60.48 MB
Page 1126 of 1640
Intake Air System
System Description
The system supplies air for all engine needs. It consists of the intake air pipe. Air Cleaner (ACL), intake air duct, throttle
body. Idle Air Control (IAC) Valve, fast idle thermo valve, and intake manifold. A resonator in the intake air duct provides
additional silencing as air is drawn into the system.
FAST
IDLE
THERMO
VALVE
ECM
IAC VALVE
TO PGM-FI MAIN
RELAY
THROTTLE
VALVE
INTAKE
AIR DUCT
ACL
THROTTLE
VALVE
DASHPOT
CONTROL
DIAPHRAGM
THROTTLE
VALVE
RESONATOR
DASHPOT
CHECK
VALVEProCarManuals.com
Page 1128 of 1640
Intake Air System
Inspection/Adjustment
1. Warm up the engine to normal operating tem- perature (the cooling fan comes on).
2. Check that the throttle cable operates smoothly
with no binding or sticking. Repair as necessary.
3. Check cable free play at the throttle linkage. Cable
deflection should be 10—12 mm (0.39—0.47 in.).
Installation
1. Fully open the throttle valve, then install the throt-
tle cable in the throttle linkage and install the cablehousing in the cable bracket.
2. Warm up the engine to normal operating temperature (the cooling fan comes on).
4. If deflection is not within specs, loosen the locknut and turn the adjusting nut until the deflection is as
specified.
5. With the cable properly adjusted, check the throttle valve to be sure it opens fully when you push the
accelerator pedal to the floor. Also check the throt-
tle valve to be sure it returns to the idle position whenever you release the accelerator. 3. Hold the cable sheath, removing all slack from the
cable.
4. Turn the adjusting nut until it is 3 mm (0.12 in.)
away from the cable bracket.
5. Tighten the locknut. The cable deflection should now be 10–12 mm (0.39–0.47 in.). If not, see
inspection/adjustment.
CABLE
BRACKET
LOCKNUT
10 N .
m (1.0kg-m,
7 Ib-ft)
3 mm
(0.12 in.)
ADJUSTING
NUT
DEFLECTION
10–12
mm
(0.39–0.47
in.)
ADJUSTING NUT
CABLE
BRACKET
LOCKNUT
INNER
WIRE
THROTTLE LINKAGE
LOCKNUT
ADJUSTING
NUT
CABLE
BRACKET
Throttle CableProCarManuals.com
Page 1134 of 1640
Intake Air System
Description
Satisfactory power performance is achieved by closing and opening the intake air bypass (IAB) control valves. High tor-
que at low engine speed is achieved when the valves are closed, whereas high power at high engine speed is achieved
when the valves are opened.
Intake Air Bypass (IAB) Control System
OPEN: HIGH ENGINE SPEED
INTAKE AIR BYPASS (IAB) CONTROL
SOLENOID VALVE ON
IAB
CHECK
VALVE
CLOSE: LOW ENGINE SPEED
IAB
CONTROL
DIAPHRAGM
IAB
CONTROL
VALVE
ECM
IAB
VACUUM
TANK
IAB CONTROL
SOLENOID
VALVE
TO No. 2 (15 A) FUSE
BLK/YEL
RED/BLUProCarManuals.com
Page 1141 of 1640
Positive Crankcase Ventilation (PCV) System
Description
The Positive Crankcase Ventilation (PCV) system is
designed to prevent blow-by gas from escaping to the
atmosphere. The PCV valve contains a spring-loaded
plunger. When the engine starts, the plunger in the PCV
valve is lifted in proportion to intake manifold vacuum
and the blow-by gas is drawn directly into the intake
manifold.
PCV HOSE
BREATHER PIPE
FRONT OF
VEHICLE
BLOW-BY VAPOR
FRESH AIR
PCV VALVE
If there is no clicking sound, check the PCV
valve grommet for cracks or damage. If the
grommet is OK, replace the PCV valve and
recheck.
Gently pinch here
2. At idle, make sure there is a clicking sound from the
PCV valve when the hose between PCV valve and
intake manifold in lightly pinched with your fingers
or pliers.
BREATHER
PIPE
PCV VALVE PCV HOSE
Inspection
1. Check the PCV hoses and connections for leaks
and clogging.ProCarManuals.com
Page 1142 of 1640
Emission Control System
Description
The evaporative emission controls are designed to minimize the amount of fuel vapor escaping to the atmosphere. The
system consists of the following components:
A. Evaporative Emission (EVAP) Control Canister
An EVAP control canister is used for the temporary storage of fuel vapor until the fuel vapor can be purged from the
EVAP control canister into the engine and burned.
B. Vapor Purge Control System
EVAP control canister purging is accomplished by drawing fresh air through the EVAP control canister and into a port
on the throttle body. The purging vacuum is controlled by the EVAP purge control diaphragm valve and the EVAP
control solenoid valve.
C. Fuel Tank Vapor Control System
When fuel vapor pressure in the fuel tank is higher than the set value of the EVAP two way valve, the valve opens
and regulates the flow of fuel vapor to the EVAP control canister.
EVAP PURGE CONTROL SOLENOID VALVE OFF AFTER
STARTING ENGINE
ENGINE COOLANT TEMPERATURE ABOVE
158°F
(70°C)
Evaporative Emission (EVAP) ControlsProCarManuals.com
Page 1150 of 1640
Transmission Assembly
Removal (cont'd)
20. Remove the intermediate shaft heat cover and the intermediate shaft mounting bolts.
21. Pry the intermediate shaft out of the differential. Pull and remove it.
NOTE:
Coat all precision finished surfaces with clean engine oil or grease.
Tie plastic bags over the driveshaft ends.
Corrosion resistant bolt/nut
INTERMEDIATE SHAFT
SUPPORT BASE
SET RINGReplace.
INTERMEDIATE SHAFT
22. Remove the parking brake cable holder and the wheel sensor wire clamp.
23. Remove the bolt and separate the toe control arm from the side beam (see section 18).
24. Remove the damper fork bolt (see section 18). 25. Remove the bolts and separate the lower control arm from the side beam.
26. Pry the driveshaft out of the differential. Pull and remove it.
NOTE:
Coat all precision finished surfaces with clean engine oil or grease.
Tie plastic bags over the driveshaft ends.
Corrosion resistant bolt/nut
DAMPER FORK BOLT
WHEEL SENSOR WIRE CLAMP
LOWER CONTROL ARM SELF-LOCKING NUTReplace. ADJUSTING
BOLT
ADJUSTING
CAM
SELF-LOCKING NUT
Replace.SET RING
Replace.TOE CONTROL ARM
PARKING BRAKE
CABLE HOLDER
FLANGE BOLT
TOE CONTROL ARM
SELF-LOCKING NUT
Replace. INTERMEDIATE SHAFT
MOUNTING BOLT
INTERMEDIATE SHAFT
HEAT COVERProCarManuals.com
Page 1151 of 1640
27. Remove the one of the upper control arm mounting bolt.
28. Remove the lower cover, change wire bracket and upper cover.
29. Remove the shift cable and select cable.
30. Remove the slave cylinder from the transmission.
NOTE: Do not operate the clutch pedal once the slave
cylinder has been removed.
31. Remove the release fork from the clutch release hanger, then hang the release fork on the clutch housing.
UPPER CONTROL ARM
DAMPER
SLAVE CYLINDER
UPPER COVER
UPPER ARM MOUNTING
BOLT
32. Remove the clutch housing cover. 33. Attach a chain hoist to the transmission hangers.
34. Place a jack under the transmission and raise the transmission just enough to take weight off mounts.
35. Remove the front engine mounting bolts on the transmission side and retighten the bolt on the engine side.
CAUTION: Loosen the front engine mounting bolt on the engine side, but do not remove it. After removing the two
bolts on the transmission side, be sure to retighten the bolt on the engine side.
36. Remove the rear transmission mounting bolts and engine stiffener.
37. Remove the transmission housing mounting bolts.
38. Pull the transmission away from the engine until it clears the mainshaft, then lower it on the transmission jack.
REAR TRANSMISSION
MOUNT
REAR TRANSMISSIONMOUNTING BOLT
TRANSMISSION JACK TRANSMISSION HOUSINGMOUNTING BOLT
ENGINE STIFFENER
CLUTCH HOUSING
COVER
TRANSMISSION HOUSING
MOUNTING BOLTS
FRONT ENGINE MOUNTING
BOLT
(Engine side)
FRONT ENGINE MOUNTING
BOLT
(Transmission side)
RELEASE FORK
COTTER PIN
Replace.
SHIFT CABLE
CHANGE WIRE
BRACKET
SELECT CABLE
LOWER COVER
Corrosion resistant bolt/nut
Corrosion resistant bolt/nutProCarManuals.com
Page 1160 of 1640
Transmission Assembly
Installation
NOTE:
Check that the two dowel pins are installed in the clutch housing.
Use
only Super High Temp
Urea
Grease
(P/N
08798-9002).
1. Place the transmission on the transmission jack, and raise it to the engine level.
2. Set the release fork to the clutch housing.
3. Install the two transmission housing mounting bolts and engine stiffener.
4. Install the three rear transmission mounting bolts.
5. Loosen the front engine mounting bolt, then install the two front engine
mounting bolts to the transmission side.
6. Remove the transmission jack.
7. Install the clutch housing cover.
Corrosion resistant bolt/nut
DOWEL PINS
(P/N
08798-9002)
REAR TRANSMISSION
MOUNTING BOLTS
12 x
1.25
mm
105 N .
m
(10.5 kg-m, 76 Ib-ft)
(P/lN 08798-9002)
TRANSMISSION HOUSING
MOUNTING BOLTS
12 x
1.25
mm
65 N .
m (6.5 kg-m, 47 Ib-ft)
FRONT ENGINE
MOUNTING BOLT
10 x
1.25
mm
60 N .
m (6.5 kg-m, 43 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)
CLUTCH HOUSING
COVER
10 x
1.25
mm
45 N.m (4.5 kg-m, 33 Ib-ft)
TRANSMISSION HOUSING MOUNTING BOLT
12 x
1.25
mm
65 N .
m (6.5 kg-m, 47 Ib-ft)
TRANSMISSION
JACK
8. Install the release fork in the release hanger, then install the slave cylinder.
9. Connect the shift cable and select cable. CAUTION: Take care not to bend the cables.
10. Install the upper cover, change wire bracket and lower cover.
11. Install the upper control arm mounting bolt.
Corrosion resistant bolt/nut
8 x
1.25
mm
22 N .
m
(2.2
kg-m,
16 Ib-ft)
UPPER COVER
COTTER PIN Replace.
6 x 1.0 mm
12 N .
m
(1.2
kg-m,
9 Ib-ft)
CHANGE
WIRE
BRACKET
8 x
1.25
mm
26 N .
m (2.6 kg-m, 19 Ib-ft)
6 x 1.0 mm
12 N .
m (1.2 kg-m, 9 Ib-ft) LOWER
COVER
UPPER CONTROL ARM MOUNTING BOLT
10 x
1.25
mm
60 N .
m (6.0 kg-m. 43 Ib-ft)
(Silicone Grease)
SLAVE CYLINDERProCarManuals.com
Page 1165 of 1640
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
Page 1166 of 1640
REVERSE,
Description
(cont'd)
AUTOMATIC TRANSAXLE (A/T) GEAR POSITION INDICATOR
A/T gear position indicator in the instrument panel shows what gear has been selected without having to look down at
the console.
ATF COOLER
With this mid-engine type car, the radiator is mounted at the front of the car, so the ATF cooler is installed directly on
the transmission housing. Position
Description
PARK
REVERSE
NEUTRAL
DRIVE
THIRD
SECOND
FIRST
Rear wheels locked; parking pawl engaged with parking gear on countershaft.
All clutches released.
Reverse; reverse selector engaged with countershaft reverse gear and 4th clutch locked.
All clutches released.
General driving; starts in low speed, shifts automatically, depending on vehicle
speed and throttle position. Downshifts'through 3rd, 2nd and 1st on deceleration
to stop.
The lock-up mechanism comes into operation in 2nd, 3rd and 4th.
Driving in 3rd gear; stays in 3rd gear, does not shift up and down.
For climbing or downhill and light engine braking on high speed condition.
The lock-up mecharism comes into operation.
Driving in 2nd gear; stays in 2nd gear, does not shift up and down.
For engine braking or better traction starting off on loose or slippery surface.
Driving in 1st gear, stays in 1st gear, does not shift up.
For engine braking.
GEAR SELECTION
The selector lever has seven positons:
PARK,
NEUTRAL,
1st through 4th gear positions,
3rd
gear,
2nd gear and
1st gear.
Starting is possible only in
and
position through use of a slide-type, neutral-safety switch.
ProCarManuals.com