MAZDA 626 1987 Workshop Manual

IDLE ADJUSTMENT 4B
76G04B-034
76G04B-035
Idle mixture
Automatic
Control
Function
Engine Control Unit

IDLE
ADJUSTMENT
IDLE SPEED
Preparation
1) Check the condition of the engine (plugs, leaks in
hoses, etc.).
2) Make sure all accessories are OFF.
3) Warm up the engine and run it for three minutes
at 2,500—3,000 rpm in neutral.
4) Check the initial ignition timing and adjust if
necessary.
Inspection and Adjustment
Caution
Disconnect the air bypass solenoid connec-
tor when checking and adjusting the idle
speed.
1. Check that the idle speed is within specification.
Specification:
MTX—800 +58 rpm
ATX—900 +58 rpm (P range)
2. If the idle speed is not within specification, remove
the blind cap from the throttle body and adjust it
by turning the air adjust screw.
IDLE MIXTURE
Because an automatic compensation function
for air/fuel mixture is built into the engine con-
trol unit, it is not necessary to check and adjust
the idle mixture.
86U04A-049
4B-29

4B INTAKE AIR SYSTEM
INTAKE AIR SYSTEM
76G04B-036
This system controls the air required by the engine for operation. The system consists of the air duct,
air cleaner, air flow meter, throttle body, dynamic chamber, and intake manifold.
COMPONENT DESCRIPTIONS
Component Function Remarks
Air cleaner
Filters
air
into throttle body

Air flow meter
Detects amount
of
intake air;
sends signal
to
engine control unit Intake
air
thermo sensor and fuel pump
switch are integrated

Throttle body
Controls intake
air
quantity Integrated throttle sensor and idle switch

76G04B-037
4B—30

INTAKE AIR SYSTEM 4B
REMOVAL
Caution
Before removing the following parts, release the fuel pressure from fuel system to reduce
the possibility of injury or fire. (Refer to page 4B—45.)
Remove in the sequence shown in the figure.
1. Air flow meter connector
and secondary air hose
2. Air cleaner
3. Air duct
4. Resonance chamber
5. Air flow meter
6. Air hose
7. Vacuum hoses, air hoses,
and water hoses
8. Accelerator cable
9. Throttle sensor connector
10. Throttle body
11. EGR modulator valve
12. Air hose
13. Air bypass solenoid valve
76G04B-038
14. Intake manifold bracket
15. Dynamic chamber bracket
16. Fuel return pipe
17. Dynamic chamber
18. Injector connector
19. Delivery pipe assembly
20. Air valve
21. Intake manifold and gaskets
4B—31

4B INTAKE AIR SYSTEM
69G04A-059
86U04A-053
79G04D-084
PARTS INSPECTION
Air Cleaner Element
1. Check the condition of the air cleaner element.
2. Replace, if necessary.
Caution
Do not use the compressed air to clean the
air cleaner element.
Accelerator Cable
1. Inspect the deflection of the cable. If the deflec-
tion is not within 1—3 mm (0.04—0.12 in.), ad-
just by turning nuts A.
2. Depress the accelerator pedal to the floor and con-
firm that the throttle valve is fully opened. Adjust
by turning bolt B if necessary.
Throttle Body
Caution
a) The throttle adjust screw is preset and
sealed.
Do not attempt to adjust it.
If there is a malfunction of the throttle ad-
just screw, lever, or throttle valve, replace
the throttle body as an assembly.
b) Do not remove the thin sealing coating from
the throttle valve or bore.
79G04D-085
4B-32

INTAKE AIR SYSTEM 4B
76G04B-039
D C B E\\ I I A
p 'V > "
F G
76G04B-040
76G04B-041
1. Check that the throttle valve moves smoothly when
the throttle lever is moved from fully closed to fully
open.
2. Warm up the engine and run at idle.
3. Check the vacuum generated at each port as
shown in the following table.

~ —Condition
Port (Connected to) ——____ Idle Other
A (solenoid valve, EGR) No Yes
B (distributor, advance) No Yes
C (EGR modulator valve) No Yes
D (water thermo valve) No Yes
E (vacuum switch valve
&
charcoal canister) Yes
F (distributor, retard
& air
control valve) Yes
G (distributor, advance) Yes

4. If vacuum is not obtained as in the table, clean the
necessary port.
Dynamic Chamber
1. Visually check the dynamic chamber for damage.
2. Replace, if necessary.
Intake Manifold
1. Visually check the intake manifold for damage.
2. Replace, if necessary.
76G04B-042
4B—33

4B INTAKE AIR SYSTEM
INSTALLATION
install in the reverse order of removal.
Torque Specification
8—11 N-m (0.8—1.1 m-kg, 5.8—8.0 ft-lb)
19—25 N m (1.9—2.6 m-kg, 14—19 ft-lb)
19—25 N m (1.9—2.6 m-kg, 14—19 ft-lb)
8—11 Nm (0.8—1.1 m-kg, 5.8—8.0 ft-lb)
8—11 N-m (0.8—1.1 m-kg, 5.8—8.0 tt-lb)
a® ^£-5—7 N-m ;'(0.5—0.7 m-kg, 13.6—5.1 ft-lb)
8—11 Nm (0.8—1.1 m-kg 5.6—8.0 ft-lb)
19—25 N-m '41.9—2.6 m-kg, tf>14—19 ft-lb)
8—11 N-m (0.8—1.1 m-kg, 5.8—8.0 ft-lb)
8—11 N-m (0.8—1.1 m-kg 5.8—8.0 ft-lb)
4B—34
76G04B-125

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