Page 337 of 1681

In
Intake Air System
Throttle Body
$;
Description
The throttle body is of the single barrel side-draft type.
The lower portion of the throttle valve is heated by
engine coolant from the cylinder head. The idle adjusting
screw which increases/decreases bypass air is located on
the top ot the thronle body.
IDLE ADJUSTINGSCREW
THROTTLESTOP SCREW(Non-adjustable)
FAST IDLE
| | .o clearance. THRoTTLE SToP scREw
{ | | _ .lDonotadiust)
| | y:::::::T,"9":::.'"Tl::f ,::i1::"1" fllyll-'n"
VALVE {A/T model onlv}
Inspection
1. Start the engine. Hold the engine at 3,000 rpm with
no load {in Park or neutral) until the radiator fan
comes on, then let it idle.
2. Stop the engine, and check that the throttle cable
operates smoothly without binding or sticking.
. lf the throttle body pon is clogged, clean it with
carburetor cleaner.
. lf there are any abnormalities in the above steps,
check for:
Excessive wear or play in the throttle valve shaft.- Sticky or binding throttle lever at full close posi-
tion.- Clearance between throttle stop screw and throt-
tle lever at fullclose position.
81881, Bl8Cl engines:
There should beno clearance.
818C5 engine:THROTTLE LINK
There should be
throttle valve shaft or if the shaft is binding or sticking.
glL-
Page 338 of 1681
Disassembly
NOTE:
. The throttle stoD screw is non-adiustable.
. After reassembly, adjust the th rottle ca ble (page 11-130, 131),andA/Tthrottlecontrol cable (section l4)Ior cars with A/T.. The TP sensor is not removable.
IOLE ADJUSTINGSCREW
FAST IDLETHERMOVALVE {A/T model onlylInspectaon, page 1 1-l 10
-l
12.2 kgf.m, 16 lbf.ft)
1 1-133
Page 339 of 1681
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Intake Air System
Intake Air Bypass (lAB) Control System [818C1 enginel
Descriplion
Two air intake oaths are erovided in the intake manifold to allow the selection of the intake path most favofable for a given
engine speed.
Satjsfactory power performance is achieved by closing and opening the intake air bypass (lAB) control valves. High torque
at low RpM is acheived when the valves are closed, whereas high power at high RPM is achieved by when the valves are
opened.
IAB CONTROLVALVES
ECM
illf1l
i 11-134
--_
CHECI( VALVE
Page 340 of 1681

Troublsshooting
IAB CONTROLDIAPHRAGM
Inapection ot IAB Control System.
Chack {or vacuum at idle:1. Stan the engine and allow itto idle.2. Romove the vacuum hose fromthe IAB control diaphragm andconnect vacuum gauge to thenose,
Check to. vacuum at IAB vacuumttnl;Remove No. 13 vacuum hose fromthe IAB vacuum tank, then checkfor vacuum at the IAB vacuumtank.
Repair th€ blockage or vacuuml6ak between the IAB vacuumtenk 6nd the intake manifold.
Check for an open in the wirellAB SOL line):1. Turn the ignition switch OFF.2. Disconnect the IAB controlsolenoid valve 2P connector.3. Turn the ignition switch ON (ll).4. Measure vohage between theIAB control solenoid valve 2Pconnector terminals No, 1 andNo.2.
ls there battery voltage?
Chack for rn op€n or 3hort in thewire (lAB SOL line):Measuro voltage between bodyground and the IAB controlsolenoid valve 2P connector termi-nai No. 1.
IAB SOL(RED/BLUI
rt./; Ir I-TD,2F-' Y\.\/ | ]IGND(BLKI
Wire side ot female terminals
IAB CONTROL SOLENOIDVALVE 2P CONNECTOR {C134)
IAB SOLIRED/BLU)
(cont'd)
11-135
(To page I'l-136)(To page 11.136)
Page 341 of 1681

I
lntake
lntake
Air System
Air Bypass (lABl ControlSystem tB18C1 enginel (cont'd)
(From page 11i135)(From page 11 135)
IAB CONTROL SOLENOID
VALVE 2P CONNECTOR (C13ir)
'._r taB sol-H, IRED/ALUI// 1 \-'lf---:----l /A\
\2Y
Wire side o{ female terminals
\
.t
Check {or vacuum at 6,000 rpm:
1, Raise engane speed to above
6,000 rpm.2. Check for vacuum at the
vacuum hose,
Disconnect the IAB control solenoidvalve 2P connector.ls there vacuum?
Substitute a known-good ECM
and recheck. lf symptom goes
away, replace the original ECM.IAB control svstom is OK.
Check lor a shon in the wire (lAB
SOL line):1. Turn the ignition switch OFF.2. Disconnect the ECM connector
A (32P).
3. Check for continuity betweenbody ground and the IAB con'
trol solenoid valve 2P connec-
torterminalNo. 1.
ls there battery voltage?
Repair open in the wire betwaonECM lA26) and the IAB controlsolenoid valve 2P connectoa.
Check tor an open in the wiro
{GND line)r1. Turn the ignition switch OFF.2. Check for continuity betweenbody ground and the IAB con-
trol solenoid valve 2P connector terminal No.2.
Repair open in the wire betweenthe IAB control solenoid valve 2Pconnector and G101.
Subdhnte a known-good ECM andrecheck. ll symptom goes away,r€place the original ECM.
\
Page 342 of 1681
Tssting
1. Check the IAB control valve shaft tor binding or sticking.
2. Check the IAB control valve for smooth movement.
3. With the engine at idle, check that @ of the IAB control valve is in close contact with the stop when vacuum hose isdisconnected.
With the engine at idle. check that @ of the IAB control valve is in close contact with the full-close screw when thevacuum hose is connected.
lf any tault is found, clean the linkage 8nd shafts with carburetor cleaner. lf the problem still exists after cleaning, dis-assemble the intake manifold and check the IAB valve body assembly.
11-137
Page 343 of 1681

t"iI
Emission Gontrol System
System Description
Three Way Catalytic Converter (TWCI
\
t
The emission control system includes a Three Way
Catalytic Converter (TWC), Positive Crankcase Ventilation
(PCV) system and Evaporative Emission (EVAP) Control
system. The emission control system is designed to meet
tederal and state emission standards.
InsDeciion
!@@ Do not smoke during this procedure. Keep
any open llame away from your work area.
1. Start the engine. Hold the engine at 3,000 rpm with
no load {in Park or neutral) until the radiator fan
comes on, then let it idle.
2. Connect a tachometer.
Check and adjust the idle speed, if necessary (see
page '11-11 ! ).
Warm up and calibrate the CO meter according to the
meter manufacturer's instructions.
Check idle CO with rhe headlights, heater blower,
rear window defogger, cooling fan, and air condition-
er off.
NOTE: {Canada) Pull the parking brake lever up.
Start the engine, then check that the headlights are
olf.
CO meter should indicste 0.17o maximum.
DescriDtion
The Three Way Catalytic Converter {TWC) is used to convert hydrocarbons (HC), carbon monoxide (CO), and oxides of
nitrogen (NOx) in the exhaust gas, to carbon dioxide (COr), dinitrogen {Nr) and water vapor.
Bl8Cl engine l818Bl, 818C5 engines is similar):
FRONT OFVEHICLE
PRIMAEYHEATEDOXYGEN SENSORIPRIMARY HO2S}
HOUSING
WAYCATALYSTS
SECONOARYHEATEDOXYGEN SENSOR{SECONDARYH02St
\
Page 344 of 1681

Three Way Catalytic Converter (TWC)
lT042O I Th" """n tool indicates Diagnostic Trouble Code (DTC) P0420: catatyst system efficiency below threshold.
Descriotion
This system evaluates the catalyst's capacity by means of the HO2S (Primary and Secondary) output during stable drivingconditions. lf deterioration has been detected during three consecutive driving cycles, the MIL comes on and DTC p0420 willbe stored.
NOTE: lf some of the DTCS listed below are stored at the same time as DTC PO42O. troubleshoot those DTCS tirst. thentroubleshoot DTC P0420.
P0136, P0139: Secondarv HO2S
P0141:Secondary HO2S Heater
Possible Cause
. TWC Deterioration
. Exhaust system leakage
Troubleshooting Flowchart
Problem verification:1. Do the ECM Reset Procedure.2. Start the engine. Hold theengine at 3,000 rpm with noload (in Park or neutral) untilthe radiator fan comes on,3. Connect the SCS service con,
4. Test drive 40 - 55 mph (64 -
88 km/h) for approx. two min-utes, Then decelerate Ior atleast 3 seconds with the throttle completely closed. Thenreduce the vehicle speed to35 mph (56 km/h), and try tohold it until the readinesscode comes on.
I
- The MIL has been report€d on.- OTC P0420 is stored.
Intermittent tailure, sFtem is OKat this time.ls DTC P0420 indicated?
Check the TWC {s6e 3ection 91.lf necessary, reolace the TWC.
11-139