MAZDA 626 1987 Workshop Manual

4 A DECELERATION CONTROL SYSTEM
76G04A-090
76G04A-091
DASHPOT (MTX)
Inspection
1. Suddenly move the throttle lever and check that
the dashpot rod comes out to its full stroke with
the throttle lever.
2. Release the throttle lever and check that it returns
slowly to the idle position after contacting the dash-
pot rod.
Adjustment
1. Warm up the engine to the normal operating tem-
perature and run it at idle.
2. Connect a tachometer to the engine.
3. Increase the engine speed to 3,000 rpm.
4. Slowly decrease the engine speed and check that
the dashpot rod touches the lever at 2,200 ±100
rpm.
5. If not within specification, loosen the locknut and
turn the dash pot to adjust.
ANTI-AFTERBURN VALVE
Inspection
1. Start the engine and let it idle.
2. Block the intake port of the anti-afterburn valve and
check that the engine speed does not change.
3. In crease the engine speed and quickly decelerate.
4. Check that air is pulled into the intake port for
1
—2
seconds after the accelerator is released.
76G04A-092
4A—50

DECELERATION CONTROL SYSTEM 4 A
MAIN AIR BLEED CONTROL SYSTEM
FE and F8 (ECE, Hong Kong, Singapore, and General)
Primary
Air/Fuel mixture—Lean Air/Fuel mixture—Rich
76G04A-093
This system prevents the additional air from being fed to the primary air bleed circuit and causes the
air/fuel mixture to become rich, improving acceleration.
Troubleshooting
Possible cause System inspection Solenoid valve Vacuum switch Water thermo
switch (Radiator)
Page 4A—52 4A—52 4A—94 4A—95
Checking order 1 2 3 4
Note
Make the system inspection first. If no problem is found, continue with the next inspec-
tion of the Troubleshooting. (Refer to pages 4A—46 or —47.)
4A—51

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