ACURA NSX 1991 Service Repair Manual

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Dashpot System

Description

The dashpot is employed to slow the closing of the throttle valve during gear shifting or deceleration.

DASHPOT

DIAPHRAGM
CHECK VALVEProCarManuals.com

Air Intake System
Dashpot System

Testing
1. Check the vacuum line for leaks, blockage or a disconnected hose.
2. Disconnect the vacuum hose from the dashpot diaphragm, and connect a vacuum pump to the

hose.
4. Connect a vacuum pump to the dashpot dia-
phragm.
VACUUM PUMP/GAUGE

A973X-041 -XXXXX
5. Apply vacuum and check that the rod pulls in and
vacuum holds. If the vacuum does not hold or the rod does not
move, replace the dashpot diaphragm and
retest.
3. Apply vacuum and check the speed the vacuum goes out.
Vacuum should go out slowly. If the vacuum holds or goes out quickly, replace
the dashpot check valve and retest.ProCarManuals.com

Chamber Volume Control System

Description

Satisfactory power performance is achieved by closing and opening the chamber volume control valves. High torque at

low RPM is achieved when the valves are closed, whereas high power at high RPM is achieved by when the valves are

opened.

CHAMBER VOLUME CONTROL SOLENOID

VALVE ON

ENGINE RPM IS ABOVE 4,800 rpm

OPEN

BLK/YEL

To No. 2 FUSE

CLOSE
CHECK

VALVE

VACUUM

TANK
RED/BLU

ECU

CHAMBER

VOLUME

CONTROL

DIAPHRAGM

CHAMBER

VOLUME

CONTROL

VALVE

(cont'd)ProCarManuals.com

Air Intake System
Chamber Volume Control Valve
Test

CAUTION: Do not adjust the chamber volume control

valve full-close screw. It was preset at the factory.

1. Check the chamber volume control valve shaft for
binding or sticking.

2. Check the chamber volume control valve for smooth movement.
3. Check that A of the chamber volume control valve is in close contact with the stopper when the
vacuum hose is disconnected from the diaphragm.

STOPPER

4. Check that B of the chamber volume control valve is in close contact with the full-close screw when
you apply 1 5" of vacuum to the diaphragm.

FULL-CLOSE

SCREW
If any fault is found, clean the linkage and shafts
with carburetor cleaner. If the problem still exists after cleaning,
disassemble the intake manifold and check the
chamber volume control valve (page 11-123).ProCarManuals.com

Chamber Volume Control System

Disassembly
12 N·m (1.2 kg-m, 9 Ib-ft)
22 N·m (2.2 kg-m, 16 Ib-ft)INTAKE MANIFOLD 22 N·m (2.2 kg-m, 16 Ib-ft)
GASKETReplace
CHAMBER VOLUME
CONTROL VALVE
GASKET

Replace

GASKET

Replace


CHAMBER
WASHER

Replace

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

Emission Control System

System Troubleshooting Guide
NOTE: Across each row in the chart, the systems that could be sources of a symptom are ranked in the order they should be inspected starting with . Find the symptom in the left column, read across to the most likely source, then refer to the page listed
at the top of that column. If inspection shows the system is OK, try the next most likely system , etc.

PAGE
126

128

134

135
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System Description
Tailpipe Emission
The emission control system includes a three-way catalytic converter, exhaust gas recirculation (EGR) system,
crankcase ventilation system and evaporative control

system.

The emission control system is designed to meet federal and
state emission standards.
Inspection

Do not smoke during this procedure. Keep
any open flame away from your work area.
1. Starting the engine and warm it up to normal operating temperature by driving the car on theroad.
2. Connect a tachometer.
3. Check idle speed and adjust the idle speed, if necessary (page 11-84).
4. Warm up and calibrate the CO meter according to the meter manufacturer's instructions.
5. Check idle CO with the headlights, heater blower, rear window defogger, cooling fan, and air conditioner off.
CO meter should indicate 0.1 % maximum.ProCarManuals.com

Emission Control System

Catalytic Converter

Description

The 3-way catalytic converter is used to convert hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the
exhaust gas, to carbon dioxide (CO2), dinitrogen (N2) and water vapor.

HOUSING

CATALYSTProCarManuals.com

Inspection
If excessive exhaust system back-pressure is suspected, remove the catalytic converter from the car and make a visual

check for plugging, melting or cracking of the catalyst. Replace the catalytic converter if any of the visible area is damag-

ed or plugged.

HEAT SHIELD

GASKET
Replace.

34 N·m
(3.4 kg-m,

25 Ib-ft) 34 N·m (3.4 kg-m, 25 Ib-ft)
HEAT SHIELD 10 N·m (1.0 kg-m, 7 Ib-ft)
HEAT SHIELDFRONT
CATALYTIC

CONVERTER

Removal/Installation, Section 9

Inspect housing for cracks or

other damage.
Inspect element for clogging by
looking through the inside.

FRONT OF
VEHICLE

GASKET
Replace.
34 N·m
(3.4 kg-m,

25 Ib-ft)

REAR

CATALYTIC
CONVERTER
Removal/Installation, Section 9
Inspect housing for cracks or
other damage.
Inspect element for clogging by
looking through the inside.

34 N·m (3.4 kg-m, 25 Ib-ft)
10 N·m (1.0 kg-m, 7 Ib-ft)
HEAT SHIELDProCarManuals.com