1987 MAZDA 626 Workshop Manual

4 A DECELERATION CONTROL SYSTEM
Solenoid valve (for main air bleed control system)
76G04A-094
76G04A-095
76G04A-191
System Inspection
1. Disconnect the vacuum switch connector.
2. Make sure that radiator coolant temperature is be-
low 17°C (63°F).
3. Disconnect the upper vacuum hose from the sole-
noid valve.
4. Place a finger over the solenoid valve open port
and check that vacuum is not felt when engine is
running.
5. Warming up the engine.
6. Place a finger over the same open port of the sole-
noid valve and check that weak vacuum is felt.
7. Reconnect the vacuum switch connector.
8. Check that weak vacuum is felt at the open port
of the solenoid valve at idle.
9. Accelerate the engine rapidly and check that vacu-
um is not felt.
Solenoid Valve (A/C)
1. Disconnect vacuum hose A (White) from the car-
buretor.
2. Disconnect vacuum hose B from the solenoid
valve.
3. Disconnect the solenoid valve connector.
4. Blow air through the valve from hose A and check
that it comes out of port C.
5. Apply 12V and ground to the solenoid valve with
jumper wires.
6. Blow air through the valve from hose A and check
that air not come out.
7. Replace if necessary.
76G04A-192
4A—52

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

4A
AIR
INJECTION SYSTEM
AIR INJECTION SYSTEM (EXCEPT GENERAL AND MIDDLE EAST)
Reed valve
76G04A-107
To achieve oxidization of CO and HC, the reed valve injects secondary air into the exhaust manifold.
TROUBLESHOOTING
Possible cause
Reed valve Air injection
\ Page pipe
Symptom 4A—59 4A—59
Fails emission test 1 2
76G04A-108
4A-58

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