1987 MAZDA 626 check engine

INTAKE AIR SYSTEM 4C
76G04C-054
76G04C-055
76G04C-056
Removal Note
Water hose
Before disconnecting the water hose, drain two liters
of engine coolant.
Delivery pipe assembly.
1. Separate the fuel return pipe from the delivery pipe
assembly.
2. Remove the delivery pipe assembly and the fuel
return pipe.
PARTS INSPECTION
Air Cleaner Element
1. Check the condition of the air cleaner element.
2. Blow out the dust with compressed air, if
necessary.
Caution
a) The air cleaner must be replaced at the in-
tervals outlined in the maintenance
schedule.
b) Never drive the vehicle without the air
cleaner element, otherwise, damage to the
air flow sensor (hot wire) will occur.
c) Never use an oil permeated air cleaner ele-
ment, otherwise, contamination of the hot
wire will occur.
4C—33

4C INTAKE AIR SYSTEM
Installation Note
Water hose spring clamps
Face the clamp end as shown in the figure.
Gasket
Use new gaskets at the intake manifold, dynamic
chamber, and throttle body.
86U04A-056
• . v 1
Engine 1 Ml' ' •-
hanger ^ •
• i::£?^Solenoid valve bracket
Air cleaner. r^I. ^jUvW;
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Ground harnesses
Make sure that the ground harnesses are tightened
securely at the following positions.
(1) Air cleaner upper case
(2) Solenoid valve braket
(3) Engine hanger
76G04C-062
Solenoid valve connectors
Connect the solenoid valve connectors at the posi-
tions shown in the figure.
76G04C-063
Inspection after installation
1. After completing installation, fill up the engine with
the specified engine coolant.
2. Warm up the engine and run it at idle.
3. Check for any vacuum, coolant, or fuel leaks.
76G04C-064
4C-38

VIC SYSTEM 4C
VARIABLE INERTIA CONTROL
(VIC)
SYSTEM
The VIC system supplements the intake air's inertial effect to create a torque band that runs from low
rpm through the high rpm range.
The system consists of the intake manifold, shutter valves, dynamic chambers, actuator, one-way check
valve, three-way solenoid valve, and engine control unit.
Shutter valve
Shutter valve
76G04C-065
Intake Inertia Effect
The air within the dynamic chamber and intake manifold begins to flow during the first half of the air
intake process. This air flow pushes air into the cylinder by its own inertial force during the second
half of the air intake process. This improves the charging of the cylinder.
To most effectively put this inertia charging to use, the length of the manifold leading to the dynamic
chamber needs to be changed in response to the engine rpm.
Length of intake manifold Intake inertia effect
Long Effective at low and middle speed
Short Effective at high speed
The VIC system controls the length of the intake manifold travel by switching the shutter valve either
open or closed at the specified engined rpm.
expert22 fl/i* http://rutracker.org
4C—39

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.

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