1987 MAZDA 626 Workshop Manual

IDLE-UP SYSTEM 4B
IDLE-UP SYSTEM
Dynamic chamber
To engine i
lN
Water thermo |ntake air sensor thermo
sensor
E/L control unit
-D
Solenoid A
From air ^^ flow meter ~
Engine
control
unit
Atmospheric pressure sensor
HI
f
"Solenoid B
UJ m
Solenoid C
u
Adjusting screw
| A/C
H-!
relay
IGN switch
-©n
To engine
control
unit
Magnetic clutch
fftf
tr Main relay
r © ©
P/S pressure switch
76G04B-043
Air Valve
This valve is constructed so that the gate valve is opened and closed by means of a bimetal strip and
heat coil. It acts as a fast idle mechanism by opening the gate valve to increase intake air by bypass-
ing the throttle valve while engine is cold, therefore engine speed is increased to shorten the warm
up period.
Air Bypass Solenoid Valve
This valve incorporates three solenoid valves. They operate according to the signal from the engine
control unit or A/C switch in order to achieve idling stability and the optimum idle speed.
The operating conditions of each solenoid valve are as shown below.
Solenoid valve Operating condition

A A/C operated
B Intake air temp, above 55°C (131 °F)
or
vehicle
at
above 1,000
m
(3,280
ft)

C P/S operated, E/L applied, intake
air
temp, above 55°C (131 °F), pressure regulator solenoid ON
or
vehicle
at
above 1,900
m
(6,232
ft)
4B-35

4B IDLE-UP SYSTEM
COMPONENT DESCRIPTIONS
Component Function Remarks
Air bypass solenoid
valve

Controls bypass
air
amount Operates A: A/C
: ON

B: Intake
air
temp, high
or at
high
al-
titude C: P/S
:
ON, E/L applied
or
hot start

Air valve
When cold, supplies bypass
air
into
dy-

namic chamber
• Engine speed increased
to
shorten
warm-up period
• Bimetal type

Atmospheric pressure sensor

Detects atmospheric pressure; sends sig-
nal
to
engine control unit

E/L control unit
Detects electrical load applied; sends sig-nal
to
engine control unit

Engine control unit
Detects signals from input sensors and switches; controls
air
bypass solenoid valve

Intake air thermo sensor
Detects intake
air
temperature; sends sig-
nal
to
engine control unit
Installed
in air
flow meter

P/S pressure switch
Detects P/S operation; sends signal
to
engine control unit P/S:
ON
when steering wheel turnefl right
or
left

76g04b-044
4B-36

IDLE-UP SYSTEM 4B
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensors or switch.
Possible
cause
\ Page
Symptom
Air valve
Air bypass solenoid valve Engine control unit
terminal
Possible
cause
\ Page
Symptom
Air valve
Idle-up singal Adjustment
Engine control unit
terminal
Possible
cause
\ Page
Symptom
Air valve
Idle-up singal Adjustment
1S 20
Possible
cause
\ Page
Symptom 4B—38 4B—39 4B—40 4B—89 4B—90
Engine
stalls
While warming up
1 2 3 4 5
Engine
stalls After warming up
1 2 3 4

Rough Idle
While warming up
1 2 3 4 5
Rough Idle After warming up
1 2 3 4

High idle speed after warming up
1 2 3 4 5

Runs rough on deceleration
1 2 3 4

Afterburn in exhaust system
1 2 3 4 5

Fails emission test
1 2 3 4 5

76G04B-045
4B-37

4B IDLE-UP SYSTEM
AIR VALVE
Pre-inspection
1. Start the engine and run it at idle.
2. Pinch the bypass air hose and check that the en-
gine rpm drops.
When engine still cool RPM reduced
After warming-up RPM drop within
200 rpm
3. If the speed is not reduced when cold, check the
air valve, or check for vacuum leaks at the bypass
air hose.
4. If the speed drop is more than 200 rpm when
warm, check the air valve and current to the valve.
Inspection of Terminal Voltage
1. Disconnect the connector from the valve.
2. Remove the rubber boot from the connector.
3. Start the engine and run it at idle.
4. Check that there is battery voltage at terminal (WY),
using a voltmeter.
5. If not correct, check the circuit opening relay and
wiring harness.
76G04B-046
Inspection of Air Valve
1. Check the valve for operation.
Temperature 20°C (68°F) Valve open
(When engine cool)
After warming-up Valve closed
2. Replace valve if faulty.
76G04B-047
4B—38 expert22 Arm http://rutracker.org

IDLE-UP SYSTEM 4B
AIR BYPASS SOLENOID VALVE
Inspection of Idle-up Signal
A/C
1. Warm up the engine and run it at idle.
2. Connect a voltmeter between terminal A and
ground.
3. Turn the A/C and blower motor switches ON.
4. Check that the meter shows battery voltage.
5. If not correct, check the A/C relay, A/C switch,
blower motor switch, fuse,and wiring harness.
76G04B-048
P/S
1. Warm up the engine and run it at idle.
2. Attach a voltmeter between the terminal F and
ground.
3. Turn the steering wheel all the way to either the
right or left.
4. Check that the meter shows OV.
5. Release the steering wheel.
6. Check that the meter shows battery voltage.
7. If not correct, check the P/S pressure switch (Re-
fer to page 4B—92) and wiring harness.
76G04B-049
High altitude compensation
1. Warm up the engine and run it at idle.
2. Connect a vacuum pump to the atmospheric pres-
sure sensor.
3. Connect a voltmeter between the terminals shown
in the following table and ground.
4. Apply vacuum to the atmospheric pressure sen-
sor as shown in the table using a vacuum pump.
5. Check that the voltmeter shows OV.
76G04B-050
J
O
6. Release the vacuum.
7. Check that the voltmeter shows battery voltage.
8. If not correct, check the atmospheric pressure sen-
sor (Refer to page 4B—99) and wiring harness.
Terminal Vacuum Amount

F Approx. 155 mmHg (6.10 inHg)
D Approx.
85
mmHg (3.35 inHg)

76G04B-051
4B-39

4B IDLE-UP SYSTEM
76G04B-052
76G04B-053
76G04B-054
Hot idle compensation
1. Warm up the engine and run it at idle.
2. Connect a voltmeter between the terminal F, D and
ground.
3. Remove the air cleaner upper case assembly.
4. Heat the intake air thermo sensor to more than
55°C
(131
°F).
5. Check that the meter shows OV.
6. If not correct, check the intake air thermo sensor
(Refer to page 4B—94).
E/L (Electrical load)
1. Warm up the engine and run it at idle.
2. Connect a voltmeter between the F terminal and
ground.
3. Apply the E/L.
E/L:
• Headlight • Rear defroster
• Electrical fan motor
• Blower motor (3rd or 4th position)
4. Check that the meter shows OV.
5. If not correct, check the electrical load control unit
(Refer to page 4B—93).
Adjustment
1. Warm up the engine and run it at idle.
2. Turn all accessories OFF.
3. Connect a tachometer to the engine.
4. Disconnect the air bypass solenoid valve con-
nector.
5. Check the idle speed and adjust it if necessary.
6. Apply battery power to each BAT terminal and
ground each GRD terminal as shown in the table.
7. Check that the engine speed is within specification.
76G04B-055
Valve BAT GRD Engine speed

A (for A/C) A B 1,250—1,350
rpm

B (for high altitude and high intake
air
temp.) C D 900—1,000
rpm
(MTX)
1,000-1,100
rpm
(ATX)
C (for P/S, E/L, high intake
air
temp., high altitude and
hot
idle compensations)
E F
900—1,000
rpm
(MTX)
1,000-1,100
rpm
(ATX)

4B—40

IDLE-UP SYSTEM 4B
8. If not correct, adjust by adjusting the respective
adjusting screw.
9. If there is no idle-up, replace the air bypass sole-
noid valve.
10. Reconnect the connector to the valves.
76G04B-056
4B—41

4B FUEL SYSTEM
FUEL SYSTEM
76G04B-057
This system supplies the fuel necessary for combustion at a constant pressure to the injectors. Fuel
is metered and injected into the intake manifold according to the injection control signals from the en-
gine control unit. It consists of the fuel pump, fuel filters, delivery pipe, pulsation damper, pressure
regulator, injectors, fuel pump switch (incorporated in the air flow meter), and the circuit opening relay.
The fuel pump is mounted in the fuel tank to minimize the operating noise of the fuel pump. The injec-
tors are directly supplied with battery voltage through the main relay.
4B—42