1987 MAZDA 626 Exhaust

4C
ISC
SYSTEM
TROUBLESHOOTING
Check the condition of the wiring harness and connectors 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
Symptom
Air valve P/S pres-sure switch
Solenoid
valve (Idle
speed
control)
Water
thermo
sensor
Engine control unit terminal System
In-
spection
Possible cause
\Page
Symptom
Air valve P/S pres-sure switch
Solenoid
valve (Idle
speed
control)
Water
thermo
sensor
1L 1W 2Q
System
In-
spection
Possible cause
\Page
Symptom 4C—47 4C—97 4C—48 4C—107 4C—98 4C—46
Engine
stalls
During warm up 2 — 3 4 — 5 6 1 Engine
stalls After warm up — 4 2 — 3 5 6 1
Rough
idle
During warm up 2 — 3 — — 4 5 1 Rough
idle After warm up 4 2 — 3 5 6 1
High idle speed after warm up 2 5 3 — 4 6 7 1
Runs rough on deceleration — — 2 — — 3 4 1
Afterburn in exhaust system 2 — 3 — — 4 5 1
Falls emission test 2 3 — — 4 5 1
76g04c-079
System Inspection
(Air valve)
1. Ground the test connector (Green, 1-pin) with a
jumper wire.
2. Disconnect the ISC valve connector (Gray, 2-pin)
at idle while the engine is cold.
3. Note the engine speed and reconnect the con-
nector.
4. Warm up the engine to the normal operating tem-
perature and disconnect the connector again.
5. Check that the engine speed is lower than that
when cold.
4C—46

EGR SYSTEM (UNLEADED FUEL) 4C
EXHAUST GAS RECIRCULATION
(EGR)
SYSTEM (UNLEADED FUEL)
This system introduces exhaust gas into the intake manifold to reduce NOx emissions. It operates de-
pending on the engine load, engine speed (1,500—3,500 rpm), engine coolant temperature (above
70°C, 158°F), and radiator coolant temperature (above 17°C, 63°F).
COMPONENT DESCRIPTION
Component Function Remark
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; con-trols solenoid valve (EGR)
Ne signal pick-up Detects crank angle at 180° intervals; sends signal to engine control unit
Solenoid valve (EGR) Controls vacuum to EGR control valve
Throttle sensor Detects throttle valve opening angle; sends signal to en-
gine control unit
Installed on throttle body
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)
76G04C-143
AC—17

EGR SYSTEM (UNLEADED FUEL) 4C
Apply 12V
J* Port
76G04C-147
86U04A-133
76G04C-148
4. Disconnect the solenoid valve connector.
5. Connect 12V and a ground to the terminals of the
solenoid valve.
6. Blow through the solenoid valve from vacuum hose
A.
7. Check that air flows from the air filter.
EGR Modulator Valve
1. Remove the EGR modulator valve.
2. Plug the No. 1 port and connect a vacuum pump
to the No. 3 port.
3. Blow into the exhaust gas port. Operate the vacu-
um pump and verify that vacuum is held.
4. Release the exhaust gas port and confirm that
vacuum is released.
EGR Control Valve
1. Warm up the engine and run at idle.
2. Disconnect the vacuum hose from the EGR con-
trol valve and plug it.
3. Verify that the engine runs smoothly.
4. If not correct, clean the exhaust gas passage in
the valve or replace the valve.
Note
Before replacing the EGR control valve, check
the intake air and control systems.
5. Connect a vacuum pump to the valve and apply
vacuum.
6. Verify that the engine runs roughly or stalls at more
than the specified vacuum.
Specification:
40—60 mmHg (1.6—2.4 inHg)
7. If not correct, replace the EGR control valve.
76G04C-149
4C-79

EXHAUST SYSTEM (UNLEADED FUEL) 4C
EXHAUST SYSTEM (UNLEADED FUEL)
Exhaust manifold
Catalytic converter
Main silencer
Middle pipe
76G04C-163
The catalytic converter is used to reduce CO and HC. The converter contains a compound of plati-
num and rhodium. It is a two-way catalyst type with a volume of 2,300 cc (140 cu in).
4C—87

4C EXHAUST SYSTEM (UNLEADED FUEL)
REMOVAL AND INSTALLATION
1. Remove in the sequence shown in the figure.
2. Install in the reverse order of removal.
Torque Specifications
86U04A-159
4. Catalytic converter
5. Bracket
6. Front pipe
INSPECTION
1. Check the catalytic converter and exhaust pipe for
deterioration or restriction.
2. Check the insulation covers welded onto the cata-
lytic converter for damage.
Note
If the insulation cover is touching the catalytic
converter housing, excessive heat at the floor
will occur.
19—26 N-m (1.9—2.6 m-kg, 14—19 tt-lb)
29—39 N-m (3.0—4.0 m-kg, 22—29 ft-lb)
34—49 N-m (3.5—5.0 m-kg, 26—36 ft-lb)
39—57 N-m (4.0-5.8 m-kg, 29—42 ft-lb)
37—52 N m (3.8—5.3 m-kg, 27—38 ft-lb) 8—11 N-m 8—1.1 m-kg, 69—95 In-lb)
N-m .3 m-kg, 38 ft-lb)
1. Main silencer
2. Middle pipe
3. Pre-silencer
86U04A-160
4C—88

EXHAUST SYSTEM (LEADED FUEL) 4C
EXHAUST SYSTEM (LEADED FUEL)
Pre silencer (No.1)
Main silencer
Middle pipe
76G04C-164
4C-89

4C EXHAUST SYSTEM (LEADED FUEL)
REMOVAL AND INSTALLATION
1. Remove in the sequence shown in the figure.
2. Install in the reverse order of removal.
Torque Specifications
1. Main silencer
2. Middle pipe
3. No. 2 pre-silencer
76G04C-165
4. No. 1 pre-silencer
5. Bracket
6. Front pipe
4C—90

4D
FUEL AND EMISSION
CONTROL SYSTEM
(DIESEL)
OUTLINE 4D— 2
SPECIFICATIONS 4D— 2
TROUBLESHOOTING GUIDE 4D— 3
ON-VEHICLE MAINTENANCE 4D— 4
AIR CLEANER ELEMENT 4D— 4
WATER DRAINING 4D— 4
AIR BLEEDING 4D— 4
INJECTION TIMING 4D— 5
IDLE SPEED 4D— 6
EXHAUST SMOKE 4D— 6
INTAKE AIR SYSTEM 4D— 7
STRUCTURAL VIEW 4D— 7
AIR DUCT AND AIR CLEANER 4D— 8
INTAKE MANIFOLD 4D— 9
SUPERCHARGING SYSTEM (RF-CX) 4D-10
TROUBLESHOOTING GUIDE 4D—10
ON-VEHICLE INSPECTION 4D—11
COMPREX SUPERCHARGER 4D—13
STARTING VALVE 4D—15
INTERCOOLER 4D—16
BOOST AIR TEMPERATURE SENSOR 4D—17
EXHAUST SYSTEM 4D—18
STRUCTURAL VIEW 4D—18
EXHAUST MANIFOLD 4D—19
EXHAUST PIPE AND MAIN SILENCER .... 4D—20
FUEL SYSTEM 4D—21
STRUCTURAL VIEW 4D—21
FUEL FILTER 4D—22
SEDIMENTER (GENERAL) 4D—22
WATER LEVEL SENSOR 4D—23
INJECTION PUMP 4D—24
INJECTION NOZZLE 4D—31
FUEL TANK 4D—34
76G04D-001