MAZDA 626 1987 Workshop Manual

7C VIC SYSTEM
COMPONENT DESCRIPTION
Component Function Remark
Dynamic chamber Provides chamber for VIC system operation Integrates one-way check valve
Engine control unit Monitors engine rpm, controls solenoid valve Unleaded fuel: ON at above 5200 rpm Leaded fuel: ON at above 5400 rpm
Intake manifold Provides short and long length of intake travel Integrates shutter valve
One-way check valve Holds vacuum in vacuum chamber Installed between dynamic chamber and vacuum chamber
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to control unit Installed in distributor
Solenoid valve (Vlfc) Controls vacuum to shutter valve actuator
Shutter valve Closes short intake port
Shutter valve actuator Actuates shutter valve according to
vacuum from solenoid valve
76G04C-066
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensor or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible cause
\Page\.
Symptom
Vacuum chamber (Vacuum leak)
Shutter valve actuator
One-way check valve
Solenoid valve (VIC) Engine control unit (1C)
System
Inspection
Possible cause
\Page\.
Symptom
Vacuum chamber (Vacuum leak)
Shutter valve actuator
One-way check valve Vacuum ' Electric signal | signal
Engine control unit (1C)
System
Inspection
Possible cause
\Page\.
Symptom 4C—42 4C—41 4C—43 4C—42 4C-98 4C—41
Rough idle
During warm up 2 3 4 — — — 1 Rough idle After warming up 2 3 4 — — — 1
Poor acceleration, hesitation,
or lack of power 6 5 7 2 3 4 1
Poor fuel consumption 6 5 7 2 3 4 1
76G04C-067
4C—40

VIC SYSTEM 4C
System Inspection
1. Warm up the engine to normal operating temper-
ature and run it at idle.
2. Check that the rod has been pulled into the ac-
tuator.
76G04C-068
3. Increase the engine speed and check that the rod
is released above specification.
Specification:
Approx. 5,200 rpm....Unleaded fuel
Approx. 5,400 rpm....Leaded fuel
76G04C-069
Shutter Valve Actuator
1. Disconnect the vacuum hose from the actuator,
and connect a vacuum pump to the actuator.
2. Apply approx. 200 mmHg (7.9 inHg) vacuum
and check that the rod is pulled into the actuator.
76G04C-070
VIC Solenoid Valve
1. Disconnect the vacuum hoses from the solenoid
valve.
2. Blow through the valve from port A and check that
air flows from port B.
76G04C-071
4C—41

4C VIC SYSTEM
3. Disconnect the solenoid valve connector and con-
nect 12V and a ground to the terminals of the sole-
noid valve.
4. Blow through the valve from port A and check that
air flows from the air filter.
76G04C-072
Electrical Signal
1. Connect a voltmeter to the VIC solenoid valve (O
wire).
2. Increase the engine speed and note the voltmeter
reading.
Voltmeter reading Unleaded fuel Leaded fuel
Approx. 12V Below 5,200 rpm Below 5,400 rpm
Below 2.0V Approx. 5,100 rpm Approx. 5,300 rpm
76G04C-073
Vacuum Signal
1. Disconnect the vacuum hose from the actuator.
2. Place a finger over the port opening and check
that air is pulled in at idle.
3. Increase the engine speed above specification and
check that air is not pulled in.
Specification:
Approx. 5,200 rpm Unleaded fuel
Approx. 5,400 rpm Leaded fuel
4. Connect the vacuum hose.
76G04C-074
76G04C-075
4C-42
Vacuum Chamber
1. Disconnect vacuum hose A from the dynamic
chamber.
2. Connect the vacuum pump to the dynamic
chamber.
3. Apply vacuum and check that it is held.
4. If not correct, check the one-way check valve for
vacuum leakage. (Refer to page 4C—43.)
Note
10 mm Hg (0.39 inHg) drop per 30 seconds is
allowable.
5. If the one-way check valve is good, check the dy-
namic chamber.

VIC SYSTEM 4C
One-way Check Valve
Inspection
1. Remove the dynamic chamber.
2. Remove the one-way check valve.
3. Connect a vacuum pump as shown in the illus-
tration.
4. Apply vacuum and check that it is held.
5. Connect the vacuum pump to the opposite port.
6. Apply vacuum and check that it is not held.
7. If not correct, replace the valve.
76G04C-076
Replacement
1. Remove the dynamic chamber. (Refer to page
4C-32)
2. Remove the one-way check valve.
3. Install a new valve so that the white side
of
the valve
faces to the port A.
76G04C-210
4C-43

4C ISC SYSTEM

IDLE
SPEED CONTROL
(ISC)
SYSTEM
Air valve BAC valve (ISC valve + air valve)
ISC valve
Air passage
c=£> Coolant passage
Idle switch
Large
Bypass air
amount
Small
Characteristics of air valve
Low 50°C (122°F) High
Coolant temperature
76G04C-077
To improve idle smoothness, the ISC system controls the intake air amount by regulating the bypass
air amount that passes through the throttle body.
This system consists of the BAC valve and the control system.
The BAC valve consists of the air valve which functions only when the engine is cold (below 50°C
(122°F)) and the ISC valve which works throughout the entire engine speed range.
4C-44

ISC SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remark
A/C switch Detects air conditioner operation; sends
signal to engine control unit Switch ON when air conditioner
operating
Air valve When cold, supplies bypass air into dy-namic chamber • Engine speed increased to shorten warm-up period • Thermo wax type
• Installed in BAC valve
Clutch switch Detects in-gear condition; sends signal to engine control unit Switch ON when clutch pedal released
E/L control unit Detects that E/L is being applied; sends
signal to engine control unit
Engine control unit Detects signals from input sensors and switches; controls solenoid valve (Idle speed control)
Idle switch Detects when throttle valve fully closed;
sends signal to engine control unit
Installed on throttle body
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Neutral switch Detects in-gear condition; sends signal to engine control unit
Switch ON when in gear
P/S pressure switch Detects P/S operation; sends signal to engine control unit Switch ON when steering wheel turned right or left
Solenoid valve (Idle speed control) Controls bypass air amount • Controlled by duty signal from engine control unit • Installed in BAC valve
• Operates idle-up
Test connector For initial idle speed adjustment • Gerrn, 1-pin
• Idle speed feedback control cancelled when connector grounded
Water thermo sensor Detects coolant temperature; sends
signal to engine control unit
76G04C-078
4C—45

4C
ISC
SYSTEM
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible cause
\Page
Symptom
Air valve P/S pres-sure switch
Solenoid
valve (Idle
speed
control)
Water
thermo
sensor
Engine control unit terminal System
In-
spection
Possible cause
\Page
Symptom
Air valve P/S pres-sure switch
Solenoid
valve (Idle
speed
control)
Water
thermo
sensor
1L 1W 2Q
System
In-
spection
Possible cause
\Page
Symptom 4C—47 4C—97 4C—48 4C—107 4C—98 4C—46
Engine
stalls
During warm up 2 — 3 4 — 5 6 1 Engine
stalls After warm up — 4 2 — 3 5 6 1
Rough
idle
During warm up 2 — 3 — — 4 5 1 Rough
idle After warm up 4 2 — 3 5 6 1
High idle speed after warm up 2 5 3 — 4 6 7 1
Runs rough on deceleration — — 2 — — 3 4 1
Afterburn in exhaust system 2 — 3 — — 4 5 1
Falls emission test 2 3 — — 4 5 1
76g04c-079
System Inspection
(Air valve)
1. Ground the test connector (Green, 1-pin) with a
jumper wire.
2. Disconnect the ISC valve connector (Gray, 2-pin)
at idle while the engine is cold.
3. Note the engine speed and reconnect the con-
nector.
4. Warm up the engine to the normal operating tem-
perature and disconnect the connector again.
5. Check that the engine speed is lower than that
when cold.
4C—46

ISC SYSTEM 4C
76G04C-081
76G04C-082
Cooling fan switch
Rear defroster switch
Head light switch
Blower motor switch
ISC "valve
76G04C-083
(ISC valve)
6. Connect the ISC valve connector.
Note
a) Make sure that the initial idle speed is set
to specification.
b) All accessory must be OFF.
7. Again disconnect the ISC valve connector (engine
at normal operating temperature).
8. Check that the engine speed decreases.
9. Reconnect the ISC valve connector.
10 Remove the jumper wire from the test connector
and make sure that the idle speed is within specifi-
cations.
(Load Test)
11. Apply power steering, electrical, and air conditioner
loads and check that the idle speed is controlled
to within specifications.
Load Idle speed
P/S 750 ± 50
E/L 800 ± 50
A/C 800 ± 50
E/L and A/C 800 ± 50
BAC Valve
Air valve
1. Remove the BAC valve from the throttle body.
2. Blow air through the valve from port A and check
that air comes out of port B when the BAC valve
is cold..
3. If not correct, replace the BAC valve.
Note
Refer to "Installation" on this page for the
BAC valve installation.
86U04A-063
4C—47

4C
ISC
SYSTEM
ISC valve
1. Disconnect the ISC valve connector.
2. Connect an ohmmeter to the terminals of the ISC
valve.
3. Check the resistance.
Resistance (at 20°C (68°C)): 6.3—9.9 Q
4. If not correct, replace the BAC valve.
76UG4C-212
REMOVAL
1. Remove the screws.
2. Remove the BAC valve from the throttle body.
76G04C-085
Installation
Caution
Install a new gasket.
1. Remove any dirt or old sealant from the contact
surfaces.
2. Apply sealant to both sides of the gasket.
3. Tighten the screws.
76G04C-086
4C-48

FUEL SYSTEM 4C
FUEL SYSTEM
76G04C-087
This system supplies the necessary fuel for combustion at a constant pressure to the injectors. Fuel
is metered and injected into the intake manifold according to the injection control signals from the en-
gine control unit. It consists of the fuel pump, fuel filters, delivery pipe, pulsation damper, pressure
regulator, injectors, fuel pump control unit, and the control relay.
The fuel pump is mounted in the fuel tank to minimize the operating noise of the fuel pump. The injec-
tors directly supplied with battery voltage through the control relay. The connector of the injectors is
white to distinguish the injectors for FE DOHC from those of other engines.
Due to the installation of the steering angle transfer shaft for the 4-wheel steering (4WS) the fuel tank
of 4WS vehicles is designed with separate right and left sections. A transfer pump is used to pump
fuel from the left side to the right side.
4C—49