1987 MAZDA 626 water

4B SWITCH MONITOR FUNCTION
Headlight switch
76G04B-030
Rear defroster switch
76G04B-031
Inhibitor switch
76G04B-032
Water thermo switch circuit (not included in switch inspection)
Warning
4B—28

INTAKE AIR SYSTEM 4B
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 4B—45.)
Remove in the sequence shown in the figure.
1. Air flow meter connector
and secondary air hose
2. Air cleaner
3. Air duct
4. Resonance chamber
5. Air flow meter
6. Air hose
7. Vacuum hoses, air hoses,
and water hoses
8. Accelerator cable
9. Throttle sensor connector
10. Throttle body
11. EGR modulator valve
12. Air hose
13. Air bypass solenoid valve
76G04B-038
14. Intake manifold bracket
15. Dynamic chamber bracket
16. Fuel return pipe
17. Dynamic chamber
18. Injector connector
19. Delivery pipe assembly
20. Air valve
21. Intake manifold and gaskets
4B—31

INTAKE AIR SYSTEM 4B
76G04B-039
D C B E\\ I I A
p 'V > "
F G
76G04B-040
76G04B-041
1. Check that the throttle valve moves smoothly when
the throttle lever is moved from fully closed to fully
open.
2. Warm up the engine and run at idle.
3. Check the vacuum generated at each port as
shown in the following table.

~ —Condition
Port (Connected to) ——____ Idle Other
A (solenoid valve, EGR) No Yes
B (distributor, advance) No Yes
C (EGR modulator valve) No Yes
D (water thermo valve) No Yes
E (vacuum switch valve
&
charcoal canister) Yes
F (distributor, retard
& air
control valve) Yes
G (distributor, advance) Yes

4. If vacuum is not obtained as in the table, clean the
necessary port.
Dynamic Chamber
1. Visually check the dynamic chamber for damage.
2. Replace, if necessary.
Intake Manifold
1. Visually check the intake manifold for damage.
2. Replace, if necessary.
76G04B-042
4B—33

IDLE-UP SYSTEM 4B
IDLE-UP SYSTEM
Dynamic chamber
To engine i
lN
Water thermo |ntake air sensor thermo
sensor
E/L control unit
-D
Solenoid A
From air ^^ flow meter ~
Engine
control
unit
Atmospheric pressure sensor
HI
f
"Solenoid B
UJ m
Solenoid C
u
Adjusting screw
| A/C
H-!
relay
IGN switch
-©n
To engine
control
unit
Magnetic clutch
fftf
tr Main relay
r © ©
P/S pressure switch
76G04B-043
Air Valve
This valve is constructed so that the gate valve is opened and closed by means of a bimetal strip and
heat coil. It acts as a fast idle mechanism by opening the gate valve to increase intake air by bypass-
ing the throttle valve while engine is cold, therefore engine speed is increased to shorten the warm
up period.
Air Bypass Solenoid Valve
This valve incorporates three solenoid valves. They operate according to the signal from the engine
control unit or A/C switch in order to achieve idling stability and the optimum idle speed.
The operating conditions of each solenoid valve are as shown below.
Solenoid valve Operating condition

A A/C operated
B Intake air temp, above 55°C (131 °F)
or
vehicle
at
above 1,000
m
(3,280
ft)

C P/S operated, E/L applied, intake
air
temp, above 55°C (131 °F), pressure regulator solenoid ON
or
vehicle
at
above 1,900
m
(6,232
ft)
4B-35

FUEL SYSTEM 4B
COMPONENT DESCRIPTIONS
Component Function Remarks
Air flow meter
Detects amount
of
intake
air;

sends signal
to
engine control unit Intake
air
thermo sensor and fuel pump
switch
are
integrated

Atmospheric pressure sensor
Detects atmospheric pressure; sends sig-nal
to
engine control unit

Circuit opening relay
Voltage
for
fuel pump while engine running

Clutch switch
Detects in-gear condition; sends signal
to
engine control unit Switch
ON
when clutch pedal released

Engine control unit
Detects signals from input sensors and switches; controls injector operation

Fuel filter
Filters particles from fuel

Fuel pump
Provides fuel
to
injectors • Operates while engine running
• Installed
in
fuel tank

Idle switch
Detects when throttle valve fully closed;
sends signal
to
engine control unit
Installed
in
throttle sensor

Ignition coil (-) terminal
Detects engine speed; sends signal
to
engine control unit

Ignition switch (ST position)
Sends engine cranking signal
to
engine control unit

Inhibitor switch
Detects in-gear condition; sends signal
to
engine control unit
Switch
ON in "N" or "P"
range

Injector
Injects fuel into intake port • Controlled
by
signals from engine control unit • High-ohmic injector

Intake air thermo sensor
Detects intake
air
temperature;
sends signal
to
engine control unit Installed
in air
flow meter

Main relay
Supplies electric current
to
injectors and engine control unit

Neutral switch
Detects in-gear condition; sends signal
to
engine control unit
Switch
ON
in-gear

Oxygen sensor
Detects Oxygen concentration; sends sig-nal
to
engine control unit
Zirconia ceramic and platinum coating

Pressure regulator
Adjusts fuel pressure supplied
to
injectors

Pulsation damper
Absorbs fuel pulsation

Throttle sensor
Detects throttle valve opening angle; sends signal
to
engine control unit
Integrated idle switch

Water thermo sensor
Detects coolant temperature;
sends signal
to
engine control unit

Water thermo switch
Detects radiator coolant temperature; sends signal
to
engine control unit ON: above 17°C (63°F)

76G04B-058
4B—43

4B FUEL SYSTEM
TROUBLESHOOTING
Check
the
condition
of
the wiring harness and connectors before checking
the
sensors
or
switches.
Possible
cause
Page

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sensor

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w
Water
thermo
switch

Q.
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3 Q.
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Injector

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aj
Engine
con-
trol unit terminal
< £
8
<
Q. Oxygen

sensor

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M Water
thermo
switch
3
u.
Injector
3
u. 3C
3E
3B
Symptom 4B-94 4B-99 4B—98 4B-95 48—97 4B-97 4B-49 4B-S1 4B-48 4B-90 4B-90
Hard start
or
won't start (Cranks
OK)
5 4 1 3 2

Engine While warming
up
4 3 2 1 5

stalls After warming
up
1 3 2 4

Rough Idle While warming
up
4 3 2 1

Rough Idle After warming
up
1 2 4 3

Poor acceleration, hesitation,
or

lack
of
power
1 3 4 2

Runs rough
on
deceleration
1 2

Afterburn
in
exhaust system
1 2

Poor fuel consumption
5 6 4 3 2 1

Falls emission test
1 2

Engine stalls
or
rough after
hot
starting
1 3 2

76G04B-059
4B—44

FUEL SYSTEM 4B
PRESSURE REGULATOR CONTROL SYSTEM
Water thermo sensor
*
Fuel
(To fuel tank)
76G04B-072
To prevent percolation of the fuel during idle after the engine is restarted, vacuum is cut to the pres-
sure regulator, increasing the fuel pressure.
Specified time: Approx. 120 sec.
Operating condition: Coolant temperature — above 70°C (158°F)
Intake air temperature — above 10°C (50°F)
4B—53

4B FUEL SYSTEM
COMPONENT DESCRIPTIONS
Component Function Remarks
Engine control unit Detects signals from input sensors and
switches; controls solenoid valve (Pres-
sure regulator control)
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit Installed in throttle sensor
Ignition coil (-) terminal Detects engine speed; sends signal to engine control unit
Ignition switch
(ST position)
Sends engine cranking signal to engine control unit
Intake air thermo sensor Detects intake air temperature; sends signal to engine control unit
Installed in air flow meter
Pressure regulator Adjusts fuel pressure supplied to injectors
Solenoid valve (Pres-sure regulator control) Controls vacuum line to pressure regulator Closes vacuum line when hot
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
76G04B-073
4B—54