1987 MAZDA 626 check engine

DECELERATION CONTROL SYSTEM 4 A
SLOW FUEL CUT SYSTEM [FE 8VALVE—UNLEADED FUEL]
76G04A-096
This system shuts the primary slow fuel passage to prevent run-on and overheating of the exhaust
system when the ignition switch is turned OFF or during deceleration (engine speed above 2,300
rpm and idle switch ON). The slow fuel cut solenoid is actuated by the engine control unit and ignition
switch.
Troubleshooting
Note
Make the system inspection first. If no problem is found, continue with the next inspec-
tion of the Troubleshooting Guide. (Refer to page 4A—47.)
Possible cause System inspection Slow fuel cut solenoid valve
Page 4A—53 4A—34
Check order 1 2
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 carburetor connector
terminal (BW wire).
4. Increase the engine speed to 4,000 rpm; then re-
lease the throttle lever.
5. Measure the terminal voltage.
Engine speed Voltage
Above approx. 2,300 rpm Approx. 12V
Below approx. 2,300 rpm Below 1.5V
76G04A-097
4A-53

4 A DECELERATION CONTROL SYSTEM
COAST ENRICHMENT SYSTEM [FE 8VALVE—UNLEADED FUEL]
Ignition coil
Engine
control
unit
Coast enrichment
solenoid valve
Richer air bleeds
Secondary main
air bleed
Idle switch
© e
To secondary
main jet
76G04A-098
This system opens the fuel passage to the secondary stage of the carburetor during deceleration at
engine speeds of 2,300—1,500 rpm. The coast enrichment solenoid valve is actuated by the engine
control unit.
Troubleshooting
Possible cause System Inspection Coast enrichment solenoid valve
Engine control unit terminal Possible cause System Inspection Coast enrichment solenoid valve
A B D 1
Page 4A—54 4A—55 4A—91
Checking order 1 3 2
System Inspection
1. Warm up the engine to the normal operating tem-
perature and run it at idle.
2. Connect a voltmeter to the carburetor connector
terminal E.
3. Connect a tachometer to the engine.
76G04A-099
4A—54

DECELERATION CONTROL SYSTEM 4 A
4. Lift the idle switch lever. (Idle switch ON.)
5. Increase the engine speed to 3,000 rpm then de-
celerate.
6. Check the terminal voltage as shown.
Voltage:
Above approx. 2,300 rpm Approx. 12V
Approx. 2,300 rpm—1,500 rpm Below 1.5V
Below approx. 1,500 rpm Approx. 12V
76G04A-100
Coast Enrichment Solenoid Valve
1. Disconnect the connector of the coast enrichment
solenoid valve.
2. Apply 12V to the carburetor connector terminal D
and ground terminal E as shown in the illustration.
3. Check that the coast enrichment solenoid valve
"clicks" when making and breaking the circuit. Re-
place, if necessary.
76G04A-101
4A—55

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