1987 MAZDA 626 engine

4A DECELERATION CONTROL SYSTEM
COASTING LEANER SYSTEM (F6 SINGAPORE MTX)
Coasting leaner
0 oAir
a n, © © Battery Ignition
switch Secondary
throttle valve
| / Relay
Engine control unit
Ignition coil
76G04A-102
This system consists of the coasting leaner solenoid valve, engine control unit, ignition coil, and idle switch.
When the idle switch is ON and the engine speed is more than approx. 2,100 rpm (deceleration),
the coasting leaner solenoid valve opens the air passage port to prevent afterburn in the exhaust system.
Troubleshooting
Note
Make the system inspection first. If no problem is found, continue with the next inspec-
tion of the Troubleshooting. (Refer to page 4A—47)
Possible cause System inspection Coasting leaner solenoid valve Relay
Page 4A—56 4A—57 4A—57
Checking order 1 2 3
Coasting leaner System Inspection
1. Warm up the engine and run it at idle.
2. Connect a tachometer to the engine.
3. Connect a voltmeter to the coasting leaner sole-
noid valve connector (LgB wire).
76G04A-103
4A—56

DECELERATION CONTROL SYSTEM 4 A
76G04A-104
4. lift the idle switch lever. (Idle switch ON).
5. Increase the engine speed to 3,000 rpm and then
decelerate.
6. Check the terminal voltage.
Voltage:
76G04A-105
Above approx. 2,100 rpm Below 1.5V
Below approx 2,100 rpm Approx. 12V
Coasting Leaner Solenoid Valve
1. Disconnect the connector of the coasting leaner
solenoid valve.
2. Disconnect the connector of the idle switch.
3. Apply 12V to terminal (BW wire) and ground with
a jumper wires as shown in the illustration.
4. Check that the coasting leaner solenoid valve
"clicks" when making and breaking the circuit. Re-
place, if necessary.
Relay
1. Warm up the engine and run it at idle.
2. Connect a tachometer to the engine.
3. Increase and decrease the engine speed between
1,900—2,300 rpm and check that the relay
"clicks".
4. Replace if necessary.
76G04A-106
4A—57

AIR
INJECTION SYSTEM 4A
76G04A-109
Reed Valve
1. Warm up the engine to the normal operating tem-
perature, and then stop the engine.
2. Remove the air cleaner cover and element.
3. Start the engine and run it at idle.
4. Place a thin paper over the reed valve inlet port
and check that air is pulled in.
5. Increase the engine speed to 1,500 rpm and
check that there is no exhaust gas leakage at the
inlet by placing a thin paper over the port.
6. Replace the reed valve, if necessary.
76G04A-110
Air Injection Nozzle and Pipe
1. Disconnect the hoses from the air cleaner.
2. Loosen the nuts and remove the air injection noz-
zle and air pipe.
3. Visually check the air injection nozzle and pipe.
4. Replace if necessary.
76G04A-111
4A-59

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

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

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