1987 MAZDA 626 sensor

4C TROUBLESHOOTING WITH SST
76G04C-025
Code No. 15 (Oxygen sensor) PC: Possible Cause
76G04C-026
4C—20

4C TROUBLESHOOTING WITH SST
No.36 Code (Oxygen sensor relay) PC: Possible Cause
YES
Is there continuity between Oxygen sensor relay engine control unit?
Oxygen sensor relay Engine control unit
RY 2M
NO^ PC: Open circuit in wiring harness from oxygen sensor relay to engine control unit
YES PC: • Engine control unit malfunction • Short circuit in wiring harness
76G04C-033
No.41 Code (Solenoid valve—Variable inertia control (VIC)) PC: Possible Cause
Are there poor connections in solenoid valve circuit? YES Repair or replace connector
NO
NO Is there continuity of VIC solenoid valve? NO Replace solenoid valve
YES
Is there battery voltage at RB wire of VIC solenoid valve connector?
NO PC: Open or short circuit in wiring harness from RG wire to control relay (for engine control unit)
YES
Is there continuity between VIC solenoid valve and engine control unit?
VIC solenoid valve Enaine control unit
L 1C
NO PC: Open circuit in wiring harness from VIC solenoid valve to engine control unit
YES PC: • Engine control unit malfunction • Short circuit in wiring harness
76G04C-034
4C—24

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

4C INTAKE AIR SYSTEM
REMOVAL
Caution
Before removing the following parts, release the fuel pressure from fuel system to reduce
the possibility of injury or fire. (Refer to page 4C—52.)
Remove in the sequence shown in the figure, referring to the removal note.
1. Air cleaner
2. Air flow sensor
3. Air hoses
4. Connectors (Idle switch,
ISC, Throttle sensor)
5. Water hoses
6. Vacuum hoses
7. Accelerator cable
8. Throttle body
9. Gasket
10. PCV hose
4C-32
11. Vacuum pipe assembly
(Unleaded fuel)
12. Dynamic chamber brackets
13. Connectors (Knock sensor,
Intake air thermo sensor)
14. Dynamic chamber
15. One-way check valve
16. Gasket
17. Wiring harness
(for injectors)
18. Fuel hoses
76G04C-053
19. Delivery pipe assembly
mounting bolt.
20. Heat insulator
21. Injectors
22. Delivery pipe assembly
23. EGR pipe
24. Intake manifold bracket
25. Solenoid valve
26. Intake manifold
27. Gasket
28. Air duct
29. Resonance chamber

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

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

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