1995 ACURA TL engine

Idle Control System

System Description

The idle speed of the engine is controlled by the Idle Air Control (IAC) Valve.

The valve changes the amount of air bypassing into the intake manifold in response to electric current controlled by the

PCM. When the IAC Valve is activated, the valve opens to maintain the proper idle speed.

ENGINE

COOLANT

IAC VALVE

INTAKE

MANIFOLD
PCM
From

PGM-FI

MAIN

RELAY

FAST

IDLE

THERMO

VALVE
IDLE

ADJUSTING

SCREW
VARIOUS

SENSORS

ENGINE

COOLANTProCarManuals.com

Idle Contro l Syste m
System Descriptio n (cont'd )
1. Afte r th e engine starts, th e IA C valv e open s fo r a certai n time . Th e amoun t o f ai r i s increase d t o rais e th e idl e spee d
about 150-30 0 rpm .
2. Whe n th e coolan t temperatur e i s low , th e IA C valv e i s opene d t o obtai n th e prope r fas t idl e speed . Th e amoun t o f
bypasse d ai r i s thu s controlle d i n relatio n t o th e engin e coolan t temperature .
IDLE SPEE D(rpm)
ENGIN ECOOLAN T TEMPERATUR E
3. Whe n th e idl e spee d i s ou t o f specificatio n an d th e sca n too l doe s no t indicat e Diagnosti c Troubl e Cod e (DTC ) P050 5 o r
P1508 , chec k th e followin g items :
Adjus t th e idl e spee d (se e pag e 11-114 )
Ai r conditionin g signa l (se e pag e 11-104 )
AL T F R signa l (se e pag e 11-106 )
Starte r switc h signa l (se e pag e 11-107 )
A/ T gea r positio n signa l (se e pag e 11-108 )
PS P switc h signa l (se e pag e 11-110 )
Brak e switc h signa l (se e pag e 11-112 )
Fas t idl e therm o valv e (se e pag e 11-113 )
Hose s an d connection s
IA C valv e an d it s mountin g O-ring s
4 . I f th e abov e item s ar e normal , substitut e a known-goo d IA C valv e an d readjus t th e idl e spee d (se e pag e 11-114 ).
I f th e idl e spee d stil l canno t b e adjuste d t o specificatio n (an d th e sca n too l doe s no t indicat e DT C P050 5 o r P1508 )
afte r IA C valv e replacement , substitut e a known-goo d PC M an d recheck . I f sympto m goe s away , replac e th e origina l
PCM.
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(From pag e 11-104 )
I s ther e a clickin g nois e fro m
th e A/ C compresso r clutch ?
Chec k fo r th e operatio n o f th e
A/C :1. Star t th e engine .
2 . Tur n th e blowe r switc h ON .
3 . Tur n th e A/ C switc h ON .
Doe s th e A/ C operate ?
Ai r conditionin g signa l i s OK . Chec
k fo r a n ope n i n th e wir e
(ACC line) :Momentaril y connec t th e A/ C
clutc h rela y 4 P connecto r termi -
nal No . 2 to bod y groun d wit h ajumpe r wir e severa l times . A/
C CLUTC H RELA Y CONNECTO R (C308 )
JUMPE RWIRE
Wire sid e o f
femal e terminal s
I s ther e a clickin g nois e fro m
th e A/ C compresso r clutch ? Se
e ai r conditione r inspectio n
(se e sectio n 22 ).
Repai r ope n in th e wir e betwee n
th e PC M (A8 ) an d th e A/ C clutc h
relay.
PCM CONNECTOR S
A (26P)
Chec k fo r a n ope n i n th e wir e
(AC S line) :
Measur e voltag e betwee n PC M
connecto r terminal s A2 6 an d C2 . Wir
e sid e o f femal e terminal s
I s voltag e les s tha n 1. 0 V ? Repai
r ope n i n th e wir e betwee n
th e PC M (C2 ) an d th e A/ C pres -
sur e switc h A or radiato r fa n
diode .
Substitut e a known-goo d PC M
an d recheck . I f symptom/indi -
catio n goe s away , replac e th e
origina l PCM .
Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
C (12P )
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Idle Contro l Syste m
Alternato r (ALT ) F R Signa l
This signal s th e PC M whe n th e Alternato r (ALT ) i s charging .
Is ther e approx . 5 V ?
Chec k th e operatio n o f th e ALT :
1 . Tur n th e ignitio n switc h OFF .
2 . Reconnec t th e AL T GR N 4 P
connecto r t o th e ALT .
3 . Star t th e engine . Hol d th e
engin e a t 3,00 0 rp m wit h n o
loa d (transmissio n in o r
position ) unti l th e radiato r fa n
come s on , the n le t i t idle .
4 . Measur e voltag e betwee n PC M
connecto r terminal s D 5 an d A26 .
Doe s th e voltag e decreas e whe n
headlight s an d rea r defogge r ar e
turne d on ?
Chec k fo r a n ope n in th e wir e (AL T
F line) :
1 . Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e negativ e bat -
ter y cabl e fro m th e battery .
3 . Disconnec t th e PC M connec -
tor D (22P) .4. Disconnec t th e GR N 4 P con -
necto r fro m th e ALT .
5 . Connec t th e AL T 4 P connecto r
termina l No . 2 to bod y groun d
with a jumpe r wire .6. Chec k fo r continuit y betwee n
bod y groun d an d PC M con -
necto r termina l D5 .
I s ther e continuity ?
Se e th e AL T inspectio n (se e
sectio n 23 ).
PC M CONNECTOR S
A (26P)D (22P )
LG1 (BRN/BLK )
Wire sid e o f femal e terminal s
Chec k fo r a shor t i n th e wir e (AL T
F line) :1. Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e negativ e bat -
ter y cabl e fro m th e battery .
3 . Disconnec t th e PC M connecto r
D (22P) .4. Chec k fo r continuit y betwee n
bod y groun d an d PC M con -
necto r termina l D5 .
D (22P )
Is ther e continuity ? Repai
r shor t i n th e wir e betwee nthe PC M (D5 ) and th e ALT .
Substitut e a known-goo d PC M
an d recheck . I f prescribe d voltag e
i s no w available , replac e th e origi -
nal PCM .
ALT F R signa l i s OK .
ALT GR N 4P CONNECTO R (C129 )
JUMPE R WIR E
Wir e sid e o f femal e terminal s
Repai r ope n wir e betwee n th e
PC M (D5 ) and th e ALT .
Wire sid e o f femal e terminal s
PC
M CONNECTO R D (22P )
Chec
k fo r a shor t i n th e wir e (AL T
F line) :
1 . Disconnec t th e GR N 4 P con -
necto r fro m th e ALT .
2 . Tur n th e ignitio n switc h O N (II) .
3 . Measur e voltag e betwee n PC M
connecto r terminal s D 5 an d A26 .
Inspectio
n o f AL T F R Signal .
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Starter Switch Signal

This signals the PCM when the engine is cranking.

PCM CONNECTORS

A
(26P)
C
(12P)

Wire side of female terminals

Is there battery voltage?

Is the fuse OK?
Repair short in the wire be-

tween the PCM (C6) and the

No. 9 STARTER SIGNAL (7.5

A) fuse or the PGM-FI main

relay.

Replace the No. 9 STARTER

SIGNAL (7.5 A) fuse.

Repair open in the wire between

the PCM
(C6)
and the No. 9

STARTER SIGNAL (7.5 A) fuse.
Starter switch signal is OK.
Inspect the No. 9 STARTER SIG-

NAL (7.5 A) fuse in the under-dash

fuse/relay box.
Check for an open or short in the

wire (STS line):

Measure voltage between PCM

connector terminals C6 and A26

with the ignition switch in the

start position (III).
Inspection of Starter Switch Sig-

nal.
NOTE: Transmission in or position.ProCarManuals.com

(From pag e 11-108 )
Chec k fo r a n ope n in th e wir e (AT P
P N line) :
1. Tur n th e ignitio n switc h OFF .2. Reconnec t th e 16 P connecto r
t o th e gaug e assembly .
3 . Star t th e engine .
4 . Measur e voltag e betwee n PC M
connecto r terminal s E2 4 an d
A26 wit h th e transmissio n inposition .
PCM CONNECTOR S
A (26P)E (26P)
Wire sid e o f femal e terminal s
I s ther e les s tha n 1. 0 V ? Repai
r ope n in th e wir e betwee n
the PC M (E24 ) an d the gaug e
assembly .
Check fo r a n ope n in th e wir e (AT PPN line) :Measur e voltag e betwee n PC M
connecto r terminal s E2 4 an d A2 6
with th e transmissio n i n posi -tion.
Is ther e les s tha n 1. 0 V ? Repai
r ope n in th e gaug e assem -bly.
A/T gea r positio n signa l i s OK .
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Fast Idl e Therm o Valv e
Descriptio n
T o preven t errati c runnin g whe n th e engin e i s warmin g
up , i t i s necessar y t o rais e th e idl e speed . Th e fas t idl e
therm o valv e i s controlle d b y a thermowa x plunger .
Whe n th e engin e i s cold , th e engin e coolan t surround -
in g th e thermowa x contract s th e plunger , allowin g addi -
tiona l ai r t o b e bypasse d int o th e intak e manifol d s o tha t
th e engin e idle s faster . Whe n th e engin e reache s operat -
in g temperature , th e valv e closes , reducin g th e amoun t
o f ai r bypassin g int o th e intak e manifold .
FASTIDLETHERM OVALVE
IDLEADJUSTIN GSCREW
IACVALV E
AIR BYPAS SVALVE
WAX
Inspectio n
NOTE: Th e fas t idl e therm o valv e i s factor y adjusted ; i t
shoul d no t b e disassembled .
1 . Remov e th e cove r o f th e fas t idl e therm o valve .
2 . Star t th e engine .
3.Pu t you r finge r o n th e valv e sea t are a an d mak e sur e
tha t ther e i s ai r flo w wit h th e engin e col d (engin e
coolan t temperatur e belo w 86°F , 30°C ) an d idling .
FASTIDLETHERM OVALVE
• I f not , replac e th e fas t idl e therm o valv e an d retest .
O-RING SReplace .
12 N- m(1.2 kgf-m , 8. 7 Ibf-ft )
4.
5.
Star t th e engine . Hol d th e engin e a t 3,00 0 rp m wit h n o
loa d (transmissio n in o r position ) unti l th e radia -
to r fa n come s on , the n le t i t idle .
Chec k tha t th e valv e i s completel y closed . I f not , ai r
suctio n ca n b e fel t i n th e valv e sea t area .
I f an y suctio n is felt , th e valv e is leaking .
Chec k engin e coolan t leve l an d fo r ai r i n th e engin e
coolin g syste m (se e sectio n 10 ).
I f OK , replac e th e fas t idl e therm o valv e an d
recheck .
NOTE: I f th e cove r o f fast idle therm o valv e wa s removed ,
d o th e PC M rese t procedure .
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Idle Contro l Syste m
Idle Spee d Settin g
Inspection/Adjustmen t
NOTE:
Before settin g th e idl e speed , chec k th e followin g
items :
— Th e MI L ha s no t bee n reporte d on .
— Ignitio n timin g
— Spar k plug s
— Ai r cleane r (ACL )
— PC V syste m
(Canada ) Pul l th e parkin g brak e leve r up . Star t th e
engine , the n chec k tha t th e headlight s ar e off .
1 . Star t th e engine . Hol d th e engin e a t 3,00 0 rp m wit h
no loa d (transmissio n i n o r position ) unti l th e
radiato r fa n come s on , the n le t i t idle .
2 . Connec t a OBDI I sca n too l (se e pag e 11-32 ) o r
tachometer .
• Connec t a tachomete r t o th e ignitio n contro l
module (ICM ) secondary , or.. .
TACHOMETE R
ICM
Remov e th e rubbe r ca p fro m th e tachomete r
connecto r an d connec t a tachometer .
TACHOMETE R TACHOMETE R
CONNECTOR
RUBBERCAP
3. Disconnec t th e IA C valv e connector .
4.
5 .
IA C VALV E
Start th e engin e wit h th e accelerato r peda l slightl y
depressed . Stabiliz e th e rp m a t 1,000 , the n slowl y
releas e th e peda l unti l th e engin e idles .
Check idlin g in no-loa d conditions : headlights , blow -
er fan , rea r defogger , radiato r fan , an d ai r conditione r
ar e no t operating .
Idl e spee d shoul d be :
480 5 0 rp m
(in o r position )
Adjus t th e idl e speed , i f necessary , b y turnin g th e
idl e adjustin g screw .
NOTE : Afte r adjustin g th e idl e spee d i n thi s step ,
rechec k th e ignitio n timin g (se e sectio n 23 ).
I f i t i s ou t o f spec , g o bac k t o ste p 4 .
IDL E ADJUSTIN G SCRE W
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