1987 MAZDA 626 Workshop Manual

4 A INTAKE AIR TEMPERATURE CONTROL SYSTEM
INTAKE AIR TEMPERATURE CONTROL SYSTEM
76G04A-112
This system controls air intake temperature to prevent icing and operates depending on air tempera-
ture around the control valve.
TROUBLESHOOTING
Note
Make the system inspection first. If no problem is found, continue with the next inspec-
tion of the Troubleshooting Guide. (Refer to pages from 4A—17 to 4A—22.)
FE and F8 (General, ECE, and Hong Kong) and Singapore
Possible cause
Symptom
System inspection Vacuum control
diaphragm
Intake air temperature control valve
Possible cause
Symptom 4A—61 4A—61 4A—61
Checking order 1 2 3
FE 8 Valve—Unleaded Fuel, Middle East, and F6—General
Possible cause System inspection
Page 4A—62
Checking order 1
76G04A-113
4A-60

INTAKE AIR TEMPERATURE CONTROL SYSTEM 4A
76G04A-114
76G04A-115
Intake air temperature
control valve
System Inspection
[Except Manual and Bimetal Type]
1. Disconnect the vacuum hose from the vacuum
control diaphragm.
2. Start the engine and check that vacuum is felt while
the engine is still cold.
3. Warm up the engine to the normal operating tem-
perature and check that vacuum is not felt.
Vacuum Control Diaphragm
1. Remove the air cleaner.
2. Connect the vacuum pump to the vacuum control
diaphragm.
3. Apply 160 mmHg (6.3 inHg) vacuum and check
that the shutter valve is opened to the hot position.
4. Replace the air cleaner if necessary.
Intake air temperature control valve
1. Check that the valve is closed when the bimetal
temperature is lower than specified.
Operating temperature: 30°C (86°F)
76G04A-116
C
E
75 O) o. .EE E~
—
c
60 |—c-(15.7, 13.2)
30 Z
%
(7.9, 6.61

O o>

cw
E <
Max
/Min.
20(68) 40(104) 60(140) 80(176)
Termperature °C (°F)
2. To check, suck air through the tube. If excessive
air leakage is found, replace the valve as an as-
sembly.
3. Check that the valve opens when heated.
4. Replace if necessary.
76G04A-116
4A—61

4A INTAKE AIR TEMPERATURE CONTROL SYSTEM
System Inspection
Bimetal type
[FE 8Valve—Unleaded Fuel]
Move the control valve inside the air cleaner, and
check that it moves freely and that spring force is felt.
System Inspection
Manual type
[Middle East and F6—General]
Change the summer-winter change lever and check
that it moves smoothly.
76G04A-119
4A—62

PURGE CONTROL SYSTEM 4 A
PURGE CONTROL SYSTEM
[FE 8VALVE—UNLEADED FUEL]
Vaccum switch valve -4
I
Water thermo valve
76G04A-120
This system supplies additional air to the intake manifold to improve the driveability when the engine
coolant temperature is above 50°C (122°F).
TROUBLESHOOTING
Possible cause Vacuum switch valve Water thermo valve
Page 4A—63 4A—66
Checking order 1 2
VACUUM SWITCH VALVE
1. Connect a vacuum pump to the purge control
valve as shown in the figure.
2. Blow through the valve from port A and check that
air does not come out of port B.
3. Apply 100 mm-Hg (3.94 InHg) vacuum.
4. Blow through port A and check that air comes out
of port B.
5. Replace if necessary.
76G04A-121
4A-63

4A EGR SYSTEM
EXHAUST GAS RECIRCULATION
(EGR)
SYSTEM
FE 8VALVE—UNLEADED FUEL
This system introduces exhaust gas into the intake manifold to reduce NOx emissions.
4A—64

EGR SYSTEM 4A
TROUBLESHOOTING
Note
Make the system inspection first. If no problem is found, continue with the next inspec-
tion of the Troubleshooting Guide. (Refer to pages 4A—22.)
Possible cause System inspection EGR control valve Water thermo valve
Page 4A—65 4A—65 4A—66
Checking order 1 2 3
76G04A-123
76G04A-124
76G04A-125
System Inspection
1. Start the engine.
2. Accelerate the engine while it is still cold and check
that the diaphragm of the EGR control valve does
not move.
3. Warm up the engine to normal operating temper-
ature and run it at idle.
Warning
Be careful when checking the EGR control
valve, the surrounding area is very hot.
4. Accelerate the engine and check that the di-
aphragm of the EGR control valve moves.
EGR Control Valve (ATX)
(No. 1)
1. Manually actuate the valves by pushing on the di-
aphragm with finger.
2. Check that the spring resistance is present and the
diaphragm moves freely with no sticking or
binding.
3. Warm up the engine and run it at idle.
4. Connect a vacuum pump to the valve and apply
vacuum.
5. Check that the engine runs roughly or stalls at more
than the specified vacuum.
Specification:
70—90 mmHg (2.8—3.5 inHg)
6. If not correct, replace the EGR control valve.
76G04A-126
4A—65

4A EGR SYSTEM
76G04A-127
76G04A-128
ji C
Blow here *** I
>3 l^v?
> O-—-/ 1)
Ml
r-
(No. 2)
1. Check the EGR control valve manually (same as
No. 1 valve).
2. Warm up the engine and run it at idle.
3. Connect a vacuum pump to the valve and apply
vacuum.
4. Check that the engine runs roughly or stalls at more
than the specified vacuum.
Specification:
70—90 mmHg (2.8—3.5 inHg)
5. If not correct, replace the EGR control valve.
EGR Control Valve (MTX)
1. Check the EGR control valve manually (same as
above).
2. Warm up the engine and run it at idle.
3. Connect a vacuum pump to the valve and apply
vacuum.
4. Check that the engine runs roughly or stalls at more
than the specified vacuum.
Specification:
70—90 mmHg (2.8—3.5 inHg)
5. If not correct, replace the EGR control valve.
Water Thermo Valve
1. Remove the water thermo valve from the bottom
of the inlet manifold.
2. Place the water thermo valve in a container with
water and a thermometer.
3. Gradually heat the water to 50°C (122°F).
76G04A-129
From carburetor
(A)—E
(a)-
To No.1 EGR
control valve and
vacuum switch
Wax
I— (B)
(b)
To No.2 EGR
control valve
76G04A-130
4. Blow air through the water thermo valve from (A),
and check that air comes out from (a).
5. Blow air through the water thermo valve from (B)
and check that air comes out from (b).
6. Replace if necessary.
4A—66

PCV SYSTEM 4A
POSITIVE CRANKCASE VENTILATION
(PCV)
SYSTEM
Air cleaner pcv valve
76G04A-131
This system reburns the blow-by gases and operates while the engine is running to reduce emissions.
PCV VALVE
Inspection
1. Warm up the engine to the normal operating tem-
perature and run it at idle.
2. Disconnect the PCV valve and the ventilation hose
from the cylinder head cover.
3. Block the PCV valve and check that the engine
speed drops.
4. Replace the PCV valve if necessary.
76G04A-132
4A—67