1987 MAZDA 626 engine

4C SWITCH MONITOR FUNCTION
Check connector: (Green, 6 pin)'
N negative battery
ii cable
49 H018 9A1
INSPECTION PROCEDURE
1. Warm up the engine to normal operating temper-
ature and stop it.
2. Connect the SST to the check connector (Green,
6-pin) and the negative battery terminal.
86U04A-034
Test connector: (Green, 1 pin)
3. Connect a jumper wire between the test connec-
tor (Green, 1-pin) and a ground.
4. Turn the ignition switch ON. Check if monitor lamp
illuminates as each switch is made to function as
described below.
Caution
a) If any one of the switches is activated, the
monitor lamp will stay on.
b)Do not start the engine.
76G04C-036
76G04C-037
Neutral and Clutch switch
4C—26

IDLE ADJUSTMENT 4C
Idle speed
Automatic
Control
Function
Engine Control Unit

IDLE
ADJUSTMENT
IDLE SPEED
The idle speed is controlled automatically by the
engine control unit through the idle speed con-
trol (ISC) solenoid valve, it is not necessary to
adjust the idle speed.
However, if the idle speed is not within specifi-
cation, the idle speed must be adjusted.
76G04C-044
Preparation
1) Check the condition of the engine (plugs, leaks in
hoses, etc.).
2) Make sure all accessories are OFF.
3) Warm up the engine and run it for three minutes
at 2,500—3,000 rpm in neutral.
4) Check the initial ignition timing and adjust it if
necessary.
76G04C-045
Inspection
1. Check that the idle speed is within specification
without grounding the test connector (Green,
1-pin).
Specification:
Applied load Idle speed
No load 750 ± 50 rpm
P/S load 750 ± 50 rpm
A/C and/or E/L load 800 ± 50 rpm
76G04C-046 2. If not correct, adjust the initial idle speed.
Adjustment
1. Ground the test connector (Green, 1-pin) with a
jumper wire.
2. Turn all accessories and loads OFF.
76G04C-047
4C—29

4C IDLE ADJUSTMENT
76G04C-048
Idle speed
Automatic
Control
Function
Engine Control Unit
76G04C-049
76G04C-050
3. Remove the blind cap and adjust the initial idle
speed to specification by turning the air adjust
screw.
Initial idle speed: 750 ± 50 rpm
4. After adjusting the idle speed, install the blind cap
and disconnect the jumper wire from the test con-
nector.
5. Recheck the idle speed.
6. If not within specification, check the idle speed con-
trol (ISC) system.
IDLE MIXTURE (Unleaded Fuel)
An automatic compensation function for air/fuel
mixture is built into the engine control unit, it
is not necessary to check and adjust the idle
mixture.
IDLE MIXTURE (Leaded Fuel)
Note
Before checking or adjusting the idle mixture,
check and adjust the idle speed, if necessary.
1. Insert a gas analyzer pick-up into the tail pipe.
2. Check that the CO and HC concentrations are with-
in specification.
CO concentration: 1.5 ± 0.5%
HC concentration: Less than 1,000 PPM
3. If the CO or HC concentration is not within specifi-
cation, turn the adjust screw
with
the SST to adjust.
76G04C-051
4C-30

INTAKE AIR SYSTEM 4C
INTAKE AIR SYSTEM
76G04C-052
This system controls the air required by the engine for operation. The system consists of the air duct,
resonance chamber, air cleaner, air flow sensor, throttle body, dynamic chamber, and intake manifold.
COMPONENT DESCRIPTION
Component Function Remark
Air cleaner Filters air entering throttle body Dry type
Air flow sensor Detects amount of intake air; sends signal to engine control unit Hot-wire type
Resonance chamber Minimizes intake air noise
Throttle body Controls intake air quantity Integrated throttle sensor and idle switch
4C—31

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;
Th V
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