1991 ACURA NSX sensor

CKP/CYP Sensor

Replacement

NOTE: Turn the crankshaft so fhat the No. 1 piston is at
top dead center (see page 6-19 ('91-'93) or ('94-'96))
1. Remove the timing belt (see page
6-15 ('91-'93) or ('94-'96)

2. Remove the front intake end exhaust camshaft
pulleys.
3. Remove the back cover.
4. Remove the CKP/CYP sensor from the front
cylinder head.
5. Install the CKP/CYP sensor in the reverse order of
removal.

Refer to page 6-18 ('91-'93) or ('94-'96) and 19 when

('91-'93) or ('94-'96) installing thetiming belt.

10 x
1.25
mm

70 N·m
(7.0 kg-m,

51 Ib-ft)

6 x 1.0 mm
12N·m II.2 kg-m,

9 Ib-ft) FRONT INTAKE
CAMSHAFT PULLEY

CKP/CYP

SENSOR

FRONT

CAMSHAFTS

TIMING
BELT

FRONT EXHAUST
CAMSHAFT PULLEY

10 x
1.25
mm

70 N·m
(7.0 kg-m,

61 Ib-ft)

BACK

COVER

MIDDLE COVER

6 x 1.0 mm
12N·m (1.2 kg-m.

9 Ib-ft)
LOWER COVERProCarManuals.com

Cylinder Heads

Illustrated Index (cont'd)
CAUTION:
To
avoid
damage,
wait
until
the
engine
coolant
temperature
drops
below
100°F
(39-C]
before
removing
the
cylin-

der head.

NOTE: Use new O-rings and gaskets when reassembling.

Prior to reassembling, clean all the parts in solvent, dry them, and apply lubricant to any contact parts.

REAR VARIABLE VALVE TIMING
AND VALVE LIFT ELECTRONIC CONTROL
SYSTEM (VTEC) SOLENOID VALVE

Troubleshooting, page 6-3 ('91-'93) or ('94-'96)

EXHAUST GAS
RECIRCULATI0N (EGR) VALVE

6 x 1 .0 mm
12 N·m
(1.2 kg-m.
9 Ib-ft)
8 x
1.25
mm

22 N·m
(2.2 kg-m,
16 Ib-ft)
ENGINE COOLANT
TEMPERATURE (ECT) SENSOR
18 N·m (1.8 kg-m, 13 Ib-ft)

8 x
1.25
mm
22 N·m (2.2 kg-m. 16 lb-ft)
FRONT VTEC SOLENOID VALVE

Troubleshooting. page 6-3

SEALING BOLTS

60 N·m
(6.0 kg-m,

43 lb-ft)

OIL PRESSURE

GAUSE SENDING
UNIT (section 23)

ROCKER

SHAFTS
WASHERS
Replace.

8 x
1.25
mm

22 N·m
(2.2 kg-m,16 Ib-ft)
DOWEL PIN

0-RING

Replace.

ECT SWITCH

28 N·m
12.8 kg-m.

20 lb-ft

O-RING

Replace.

O-RING

Replace.

ROCKER ARM ASSEMBLY[PRIMARY. MID, SECONDARY]

Inspection, page 6-32 ('91-'93) or ('94-'96)

ROCKER SHAFT

OIL CONTROL
ORIFICE

Remove with 5 mm

boit and clean.

FILTER
Replace.

GASKET

Replace.

O-RING

Replace.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

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 back covers.

RUBBER SEALS
REAR BACK COVER

6 x 1.0 mm
12 N·m
(1.2 kg-m,

9 Ib-ft) RUBBER SEALS
FRONT BACK COVER
RUBBER SEAL
11. Insert the dowel pins in the camshaft pulley.

12. Install the camshaft pulleys, then tighten the retain- ing bolts to the torque specified.

CAMSHAFT PULLEYS

13. Install the timing belt (see page 6-18 ('91-'93) or ('94-'96)) .
14. Adjust the valve clearance (see page 6-9 ('91-'93) or ('94-'96)).
15. Inspect the rocker arms (see pages
6-7('91-'93) or ('94-'96),8 ('91-'93) or ('94-'96)).

16. Install the head cover gasket in the groove of the
cylinder head cover. Seat the recesses for the
camshaft first, then work it into the groove around
the outside edges.

NOTE:
Before installing the head cover gasket, thor-
oughly clean the seal and the groove. When installing, make sure the head cover gasket

is seated securely in the corners of the recesses

with no gap.

HEAD COVER

GASKET Clean.

RUBBER

SEAL
CORNERS OF

THE RECESSES
CYLINDER HEAD
COVER
CORNERS OF THE RECESSES
(cont'd)

RETAINING BOLTS

10 x
1.25
mm

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

Special Tools

Ref.
No.
Tool Number Description
Qty


Page Reference
9-4('91-'93) or ('94-'96),
5 ('94-'96),
O
2
Sensor Socket Wrench
07LAA – PT50101

1ProCarManuals.com

Component Location s
Index
EXHAUS T GA S RECIRCULATIO N (EGR ) VALV E
an d LIF T SENSO R
THROTTL E POSITIO N (TP ) SENSO R
EVAPORATIV E EMISSIO N (EVAP )
PURG E FLO W SWITC H ENGIN
E COOLAN T TEMPERATUR E (ECT ) SENSO R
INTAK E AI R TEMPERATUR E (IAT ) SENSO R
CRANKSHAF T POSITION /
CYLINDE R POSITIO N
(CKP/CYP ) SENSO R
FUE L PUM P RESISTE R
Troubleshooting , pag e 11-14 1
FUE L
INJECTO R
RESISTE RTesting,page 11-13 6
THROTTL E VALV E
CONTRO L MOTO R
CONTRO L BO X
page , 11- 8
NEUTRA L SWITC H (M/ T only )
Troubleshooting , pag e 11-12 3
FRON T KNOC K SENSO R (KS2 )
REAR KNOC K SENSO R (KS1 )
SPAR K PLU G VOLTAG E
DETECTIO N MODUL E
FRON T PRIMAR Y HEATE D
OXYGE N SENSO R (HO2S )
(BAN K 2 , SENSO R 1 )
SPAR K PLU G VOLTAG E SENSO R
(buil t int o th e IGNITIO N COI L
Assy. )
FRONT SECONDAR Y HEATE D OXYGE N
SENSO R (HO2S ) (BAN K 2 , SENSO R 2 )
REA R PRIMAR Y HEATE DOXYGEN SENSO R (HO2S )
(BAN K 1 , SENSO R 1 )
REAR SECONDARY HEATED OXYGEN SENSOR
(HO2S ) (BAN K 1, SENSO R 2)
For Troubleshooting of DTC related components. see chart on page 11-52.
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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

PGM-FI Syste m
System Descriptio n
3. Fue l Cut-of f Contro l
• Durin g deceleratio n wit h th e throttl e valv e closed , curren t t o th e fue l injector s i s cu t of f t o improv e fue l econom y a t
speed s ove r 1,50 0 rpm .
• Fue l cut-of f actio n als o take s plac e whe n engin e spee d exceeds , 8,30 0 rpm , regardles s o f th e positio n o f th e throttl e
valve , t o protec t th e engin e fro m over-revving .
4 . A/ C Compresso r Clutc h Rela y
Whe n th e EC M receive s a deman d fo r coolin g fro m th e ai r conditionin g system , i t delay s th e compresso r fro m bein g
energized , an d enriche s th e mixtur e to assur e smoot h translatio n to th e A/ C mode .
5 . Evaporativ e Emissio n (EVAP ) Purg e Contro l Solenoi d Valv e
Whe n th e engin e coolan t temperatur e is belo w 153° F (67°C) , th e EC M control s th e EVA P purg e contro l solenoi d valv e
whic h cut s vacuu m to th e EVA P purg e contro l caniste r diaphragm .
6 . Intak e Ai r Bypas s (IAB ) Contro l Solenoi d Valv e
Whe n th e engin e spee d is belo w 4,80 0 rpm , th e IA B contro l solenoi d valv e is activate d b y a signa l fro m th e ECM . Intak e
ai r the n flow s throug h th e smalle r chamber , an d hig h torqu e is delivered . T o increas e ai r flo w a t engin e speed s highe r
tha n 4,80 0 rpm , th e solenoi d valv e is deactivate d b y th e ECM , an d th e intak e ai r flow s throug h th e large r chamber .
7 . Exhaus t Ga s Recirculatio n (EGR ) Contro l Solenoi d Valv e
Whe n th e EG R is require d fo r contro l o f oxide s o f nitroge n (NOx ) emissions , th e EC M supplie s groun d t o th e EG R
contro l solenoi d valv e whic h supplie s regulate d vacuu m to th e EG R valve .
EC M Fail-safe/Back-u p Function s
1 . Fail-Saf e Functio n
Whe n a n abnormalit y occur s i n a signa l fro m a sensor , th e EC M ignore s tha t signa l an d assume s a pre-programme d
valv e fo r tha t senso r tha t allow s th e engin e t o continu e t o run .
2 . Back-u p Functio n
Whe n a n abnormalit y occur s i n th e EC M itself , th e fue l injector s ar e controlle d b y a back-u p circui t independen t o f th e
syste m in orde r t o permi t minima l driving .
3 . Self-diagnosi s Functio n [Malfunctio n Indicato r Lam p (MIL) ]
Whe n a n abnormalit y occur s i n a signa l fro m a sensor , th e EC M light s th e MI L an d store s th e diagnosti c troubl e cod e
i n erasabl e memory . Whe n th e ignitio n i s initiall y turne d on , th e EC M supplie s groun d fo r th e MI L fo r tw o second s t o
chec k th e MI L bul b condition .
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