1991 ACURA NSX heater

(cont'd)
29. Remove the water passage.

O-RINGS
Replace.
CONNECTING PIPE
WATER PASSAGE

8 x
1.25
mm
22N .
m (2.2 kg-m. 16 Ib-ft)

30. Remove the cylinder head covers.
31. Turn the crankshaft so that the No. 1 piston is at top dead center (page 6-25, 26).

32.
Install
a
brace
under
the
engine, then
tilt
the
engine approximately 5° using a jack (page 6-24).
33. Remove the alternator bracket.
8 x
1.25
mm

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

10 x
1.25
mm

45N.m (4.5 kg-m.

33 Ib-ft)

ALTERNATOR
BRACKET

24. Remove the bolt from the side engine mount, then
push the side mounting bracket into the housing of
the body (page 5-27).
25. Remove the transmission mount. 26. Remove the alternator bracket stiffener (page 6-24).
27. Disconnect the knock sensor connectors, then re- move the wire holder.

6 x 1.0 mm
12N .
m (1.2 kg-m. 9 Ib-ft)
KNOCK SENSOR
WIRE HOLDER
28. Remove the heater hose and the water hoses.
WATER HOSES
HEATER HOSEProCarManuals.com

PGM-FI System

System Description

INPUTS
ENGINE CONTROL MODULE (ECM)

OUTPUTS

FRONT HO2S

REAR HO2S

MAP Sensor

CKP/CYP Sensor

ECT Sensor

TP Sensor

IAT Sensor

VSS

FRONT KS

REAR KS

Ignition Timing Adjuster

EGR Valve Lift Sensor

A/T Fl Signals

TCS Signals

Starter Signal

ALT FR Signal

Air Conditioning Signal

A/T Gear Position Switch Signal

Neutral Switch Signal (M/T)

Clutch Switch Signal (M/T)

VTEC Pressure Switch

Battery Voltage (IGN.1)

Fuel Pump Terminal Voltage
Fuel Injectors

PGM-FI Main Relay (Fuel Pump)

Malfunction Indicator Lamp

IAC Valve

A/C Compressor Clutch Relay

ICM

EVAP Purge Control Solenoid Valve

Fuel Pump Relay

EGR Control Solenoid Valve

IAB Control Solenoid Valve

Engine Compartment Fan Relay

VTEC Solenoid Valve

TCS Control Signals

FRONT HO2S HEATER

REAR HO2S HEATER

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.

Idle Air Control

Idle Air Control (IAC) Valve

When the engine is cold, the A/C compressor is on, the transmission is in gear (A/T only) or the alternator (ALT) is charg-

ing, the ECM controls current to the IAC valve to maintain correct idle speed.

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 Electron-

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

EPS Control unit
Replacement
CAUTION: Be careful not to damage the SRS wire
harnesses when servicing the control unit. 1. Remove the dashboard lower cover and glove box
and disconnect the light connector.
3. Disconnect the connectors from the EPS control
unit by removing the wire harness band.

EPS CONTROL UNIT

4. Remove the power window control unit by pulling it
toward you, then remove the EPS control unit.

5. Installation is the reverse of the removal procedure.
NOTE: Turn the ignition switch ON and check the

EPS indicator light for operation.

HEATER DUCT

2. Move the heater duct right then remove the heater

duct.
DASHBOARD LOWER COVER
GLOVE BOX

EPS CONTROL UNIT
POWER WINDOW CONTROL

UNIT

10 N ·
m

(1.0 kg-m, 7 Ib-ft)

All SRS wire harnesses and connectors
are colored yellow. Do not use electrical test equipment
on these circuits.

CONNECTORSProCarManuals.com

Carpet
Replacement
SRS wire harnesses are routed near the carpet. CAUTION:
Remove:
2. Detach the clips at the front edge (passenger's). 3, Remove the console carpet attaching screw from the heater unit (passenger's).
4. Disconnect the air duct (driver's) and air vent, then remove the carpet hooks from the dashboard inside screws.
DASHBOARD

INSIDE SCREW
CARPET
HOOK
(3)

AIR VENT

AIR DUCT
AIR VENT

CLIPS
FLOOR
CARPET
CONSOLE
CARPET

CONSOLE CARPET LEFT DASH
SENSOR
PASSENGER'S

AIRBAG
RIGHT DASH

SENSOR

SRS
MAIN

HARNESS
SRS UNIT

Side sill pad (See page 20-38) Rear side trim panel (See page 20-38)
Center armrest (See page 20-49)
Center console panel (See page 20-52)

SRS UNIT
SCREW
(cont'd)
Seats (See page 20-39)
Footrest
Under-dash fuse box lid (See page 20-38)
Side sill trim (See page 20-38)

All SRS wiring harnesses are covered with
yellow outer insulation.
Before disconnecting any part of the SRS wire
harness, install the short connectors (see page

23-328).
Replace the entire affected SRS harness assem-
bly if it has an open circuit or damaged wiring.ProCarManuals.com

Carpet

Replacement (cont'd)

5. Pull up the retainers, then remove the floor carpets.

6. Remove the console carpets.

FOOTREST

CONSOLE

CARPETS
SRS UNIT

FOOTREST MOUNTING

BOLTS

RETAINERS
RETAINERS

FLOOR CARPETS

SEAT HARNESSES

7. Installation is the reverse of the removal procedure.

NOTE:

Take care not to damage, wrinkle or twist the carpets.

Make sure the air vents are connected into the heater unit and air duct.

Make sure the seat harnesses are routed correctly.ProCarManuals.com

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

SRS wire harnesses are routed near the carpet.

CAUTION:
All SRS electrical wiring harnesses are covered with yellow outer insulation.
Before disconnecting the SRS wire harness, install the short connector on the airbag (see page 23-323).
Replace the entire effected SRS harness assembly if it has an open circuit or damaged wiring.
1. To remove the carpet, first remove the: Seats (page 20-39)
Footrest
Under-dash fuse box lid (page 20-38)

Side sill trim (page 20-38)

• Side silt pad (page 20-38)
• Rear side panel (page 20-38)
• Center armrest (page 20-38)
• Center console panel (page 20-43)

CARPETHOOK

(3)

CONSOLE CARPET

FOOTREST MOUNTING

BOLTS

5. Installation is the reverse of the removal procedure. NOTE:
Take care not to damage, wrinkle or twist the carpet.

Make sure the console carpet air vents are inserted into the heater unit and air duct.

Make sure the seat harnesses are routed correctly.

Carpet

Replacement

SRS UNIT

SRS MAIN

HARNESS FLOOR CARPETS

SRS UNIT

CONSOLE
CARPETS
CONSOLE
CARPET

FLOOR

CARPET INSIDE SCREW
CLIPS

AIR DUCT

CONSOLE

CARPET

FOOTREST

2. Pull up the retainers and carpet clips at the front edge (passenger's side), then remove the floor carpet.
3. Remove the console carpet attaching screw from the heater unit (passenger's side).
4. Remove the carpet hooks from the dashboard inside screws, then remove the console carpet.

L. DASH

SENSOR
R. DASH

SENSORProCarManuals.com

Dashboard/Center Armrest

Component Removal/Installation

SRS wire harnesses are routed near the dashboard.
CAUTION:
All SRS electrical wiring harnesses are covered with yellow outer insulation.Before disconnecting the SRS wire harness, install the short connector on the airbag (see page 23-323). Replace the entire effected SRS harness assembly if it has an open circuit or damaged wiring.
NOTE: Take care not to scratch or score the dashboard.Do not drop the screws inside the dashboard.
When prying with a flat tip screwdriver, wrap it with protective tape or shop

towel to prevent damage.

Disassemble in numbered
sequence.
CLOCK

CLOCK

CENTER AIR VENT
CENTER ARMREST
INNER PANEL
ASHTRAY

SRS UNIT

CENTER ARMREST CENTER CONSOLE

PANEL
Lift up the parking
brake lever.

HEATER CONTROL UNIT

SRS UNIT

STEREO
CASSETE/RADIO

Disconnect the

connectors.

GLOVE BOX LID
(cont'd)

DASHBOARD LOWER
PANEL (Passenger's side)
GLOVE BOX
Disconnect the connectors
TRUNK LID OPENER

MAIN SWITCH
PROTECTIVE

TAPE

CENTER AIR VENT
PROTECTIVE
TAPEProCarManuals.com