1987 MAZDA 626 coolant temperature

EGR SYSTEM 4B
EXHAUST GAS RECIRCULATION
(EGR)
SYSTEM
EGR modulator valve Solenoid valve (EGR)
86U04A-127
This system introduces exhaust gas into the intake manifold to reduce NOx in the exhaust gas. It oper-
ates depending on the engine load, engine speed (above 1,500 rpm), engine coolant temperature
(above 70°C, 158°F), and radiator coolant temperature (above 17°C, 63°F).
COMPONENT DESCRIPTIONS
Component Function Remarks
EGR control valve Recirculates portion of exhaust gas
EGR modulator valve Controls vacuum acting on EGR control
valve
Engine control unit Detects signals from input sensors and switches; controls solenoid valve (EGR)
Ignition coil (-) terminal Detects engine speed; sends signal to engine control unit
Solenoid valve (EGR) Controls vacuum line to EGR control
valve
Throttle sensor Detects throttle valve opening angle; sends signal to engine control unit Integrated idle switch
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo switch Detects radiator coolant temperature; sends signal to engine control unit
ON: above 17°C (63°F)
76G04B-102
4B-71

4B EEC SYSTEM
EVAPORATIVE EMISSION CONTROL
(EEC)
SYSTEM
Engine control unit
Solenoid valve
(Purge control)
Vacuum
switch
valve x
From water thermo valve To dynamic -chamber
Three-way
check valve
Orifice Charcoal
canister
From fuel tank
No.2 purge
control valve
Fuel tank
86U04A-136
This system stores fuel vapor generated in the fuel tank in the canister when the engine is not running.
The fuel vapor is stored in the canister until it is drawn into the dynamic chamber and burned when
the engine is started.
COMPONENT DESCRIPTIONS
Component Function Remarks
Air flow meter Detects amount of intake air; sends signal to engine control unit
Intake air thermo sensor and fuel pump
switch are integrated
Charcoal canister Stores fuel tank fumes when engine
stopped
Engine control unit Detects signals from input sensors and switches; controls solenoid valve (Purge control)
Ignition coil (-)
terminal Detects engine speed; sends signal to
engine control unit
Separator Prevents fuel from flowing into charcoal canister
Solenoid valve (Purge control) Controls vacuum line to vacuum switch valve
Three-way check valve Controls pressure in fuel tank
Vacuum switch valve Regulates evaporative fumes from canis-
ter to intake manifold
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo valve Controls vacuum applied to No.1 purge control valve and solenoid valve (Purge control)
Opens vacuum line above 54°C (129°F)
76G04B-104
4B—74

4C ISC SYSTEM

IDLE
SPEED CONTROL
(ISC)
SYSTEM
Air valve BAC valve (ISC valve + air valve)
ISC valve
Air passage
c=£> Coolant passage
Idle switch
Large
Bypass air
amount
Small
Characteristics of air valve
Low 50°C (122°F) High
Coolant temperature
76G04C-077
To improve idle smoothness, the ISC system controls the intake air amount by regulating the bypass
air amount that passes through the throttle body.
This system consists of the BAC valve and the control system.
The BAC valve consists of the air valve which functions only when the engine is cold (below 50°C
(122°F)) and the ISC valve which works throughout the entire engine speed range.
4C-44

ISC SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remark
A/C switch Detects air conditioner operation; sends
signal to engine control unit Switch ON when air conditioner
operating
Air valve When cold, supplies bypass air into dy-namic chamber • Engine speed increased to shorten warm-up period • Thermo wax type
• Installed in BAC valve
Clutch switch Detects in-gear condition; sends signal to engine control unit Switch ON when clutch pedal released
E/L control unit Detects that E/L is being applied; sends
signal to engine control unit
Engine control unit Detects signals from input sensors and switches; controls solenoid valve (Idle speed control)
Idle switch Detects when throttle valve fully closed;
sends signal to engine control unit
Installed on throttle body
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Neutral switch Detects in-gear condition; sends signal to engine control unit
Switch ON when in gear
P/S pressure switch Detects P/S operation; sends signal to engine control unit Switch ON when steering wheel turned right or left
Solenoid valve (Idle speed control) Controls bypass air amount • Controlled by duty signal from engine control unit • Installed in BAC valve
• Operates idle-up
Test connector For initial idle speed adjustment • Gerrn, 1-pin
• Idle speed feedback control cancelled when connector grounded
Water thermo sensor Detects coolant temperature; sends
signal to engine control unit
76G04C-078
4C—45

4C FUEL SYSTEM
COMPONENT DESCRIPTION
Component Function Remark
Air flow sensor Detects amount of intake air;
sends signal to engine control unit
Clutch switch Detects in-gear condition; sends signal to engine control unit Switch ON when clutch pedal released
Engine control unit Detects signals from input sensors and switches; controls injector and fuel pump operations
Fuel filter Filters fuel
Fuel pump Provides fuel to injectors • Operates while engine running
• Installed in fuel tank
Fuel pump control unit (4WS) Monitors fuel level in left section; controls transfer pump operation
G signal pick-up Detects No.1 cylinder TDC; sends signal to engine control unit Installed in distributor
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit Installed on throttle body
Ignition switch (ST position) Sends engine cranking signal to engine control unit
Injector Injects fuel into intake port • Controlled by signals from engine control unit • High-ohmic injector
Intake air thermo sensor Detects intake air temperature; send signal to engine control unit
Control relay Supplies electric current to injectors fuel pump and engine control unit
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Neutral switch Detects in-gear condition; sends signal to engine control unit
Switch ON when in gear
Oxygen sensor (Unleaded fuel) Detects oxygen concentration; sends signal to engine control unit
• Zirconia ceramic and platinum coating • Integrated heater coil
Pressure regulator Adjusts fuel pressure supplied to injectors
Pulsation damper Absorbs fuel pulsation
Throttle sensor Detects throttle valve opening angle;
sends signal to engine control unit
Installed on throttle body
Transfer pump (4WS) Pumps fuel from the left to the right side Controlled by fuel pump control unit
Transfer pump switch (4WS) Detects fuel level in left section;
sends signal to control unit
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Water thermo switch (Unleaded fuel) Detects radiator coolant temperature; sends signal to engine control unit ON: above 17°C (63°F)
76G04C-088
4C-50

4C PRC SYSTEM
PRESSURE REGULATOR CONTROL
(PRC)
SYSTEM
Distributor (Ne signal)
I Fuel
(To fuel tank)
76G04C-128
To prevent percolation of the fuel during idle after the engine is restarted, vacuum is cut to the pres-
sure regulator, increasing the fuel pressure.
Specified time: Approx. 120 sec.
Operating condition: Coolant temperature — above 70°C (158°F)
Intake air temperature — above 30°C (86°F)....Unleaded fuel
above 50°C (122°F)....Leaded fuel
4C-68

PRC SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remark
Engine control unit Detects signals from input sensors and switches; con-trols solenoid valve (Pressure regulator control)
Ignition switch
(ST position)
Sends engine cranking signal to engine control unit
Intake air thermo sensor Detects intake air temperature; sends signal to engine control unit
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Pressure regulator Adjusts fuel pressure supplied to injectors
Solenoid valve (Pres-
sure regulator control)
Controls vacuum to pressure regulator Cuts vacuum when hot
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
Idle switch Detects when throttle valve closed; sends signal to engine control unit ON at idle
76G04C-129
TROUBLESHOOTING
Check the condition of the wiring harness and connections before checking the sensors or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to pages 4C—10 and 11.)
Possible
\ cause
\ Page
Solenoid valve (Pres-sure regula-tor control)
Water thermo
sensor
Intake air
thermo
sensor
Engine con-trol unit terminal
System inspection Solenoid valve (Pres-sure regula-tor control) 2K
Symplon 4C—70 4C—107 4C-110 4C—98 4C—70
Engine stalls or runs rough after hot starting 2 3 4 5 1
76G04C-130
4C-69

DECELERATION CONTROL SYSTEM 4C
COMPONENT DESCRIPTION
Component Function Remarks
Engine control unit Detects signals from input sensors and switches; cuts fuel injection
Idle switch Detects when throttle valve fully closed; sends signal to engine control unit ON at idle
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit Installed in distributor
Water thermo sensor Detects coolant temperature; sends signal to engine control unit
76G04C-135
TROUBLESHOOTING
Check the condition of the wiring harness and connectors before checking the sensor or switches.
Note
Make the system inspection first. If no problem is found, continue with inspection of the
next system of the Troubleshooting Guide. (Refer to page 4C—10 and 11.)
Possible cause Water thermo sensor System inspection
Page 4C—107 4C—74
Checking order 2 1
76G04C-136
4C-73