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Mazda RX7. Manual - part 35

DECELERATION CONTROL SYSTEM

Article Text

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 04:58PM

ARTICLE BEGINNING

1983 Exhaust Emission Systems
MAZDA RX7 DECELERATION CONTROL SYSTEM

DESCRIPTION

The Deceleration system is designed to maintain a balanced
air/fuel mixture during deceleration. System consists of 2
anti-afterburn valves, shutter solenoid valve, coasting/shutter
valve, throttle sensor, dashpot (manual transmission models) and
connecting hoses and wiring.

OPERATION

The No. 2 anti-afterburn valve (located below air cleaner)
is actuated by the shutter solenoid valve to supply additional air
from air cleaner to intake manifold at initial deceleration to
prevent afterburning of fuel. The coasting/shutter valve work
together to supply air (coasting valve) and fuel (shutter valve)
during deceleration to prevent backfiring.

TESTING

NO. 1 ANTI-AFTERBURN VALVE

1) Warm engine to normal operating temperature and ensure
engine operates smoothly at idle. Stop engine. Disconnect air
pump-to-air control hose at air pump.
2) Disconnect electrical connectors from relief solenoid
valve (Blue color dot) and switching solenoid valve (Gray color dot).
Start engine and run at idle. Place finger over air pump-to-air
control hose.
3) Air should not be drawn in and idle speed should not
change. Disconnect vacuum sensing tube "A". The idle speed should
drop and return to normal idle when tube is connected. If valve does
not respond as outlined, replace No. 1 anti-afterburn valve.

NOTE: Before replacing No. 1 anti-afterburn valve, check auxiliary
control unit as outlined in "Mazda RX7 Auxiliary Control
Device" article in this section. Also check relief solenoid
valve and switching solenoid valve as described in "Mazda
RX7 Air Injection System" article in this section.

DECELERATION CONTROL SYSTEM

Article Text (p. 2)

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 04:58PM

Fig. 1: Testing No. 1 Anti-Afterburn Valve

NO. 2 ANTI-AFTERBURN VALVE

1) Warm engine to normal operating temperature. Disconnect
No. 2 anti-afterburn valve-to-air cleaner hose at air cleaner. Place
finger over hose and ensure air is not drawn into hose.
2) Disconnect vacuum sensing hose from No. 2 anti-afterburn
valve. Air should not be drawn into hose. Connect vacuum sensing hose
to valve; air should be drawn into anti-afterburn valve-to-air
cleaner hose for 3 seconds.
3) If air is drawn for more than 3 seconds or no air is
drawn, replace No. 2 anti-afterburn valve.

THROTTLE SENSOR

1) Warm engine to normal operating temperature. Stop engine.
Connect tachometer to engine. Disconnect throttle sensor electrical
connector, located on right side of engine (Black/Yellow and
Green/Black wires).
2) Using 2 voltmeters, connect positive lead of one
voltmeter to Light Green/Yellow wire terminal of throttle sensor
check connector.
3) Connect positive lead of other voltmeter to Green/Yellow
wire terminal of throttle sensor connector. Connect negative
terminals of voltmeters to good ground. See Fig. 2.

DECELERATION CONTROL SYSTEM

Article Text (p. 3)

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 04:58PM

Fig. 2: Testing Throttle Sensor

4) Start engine and run at 3000 RPM. Quickly decelerate
engine. Current should flow to both terminals simultaneously when
engine speed is 1000-1200 RPM.
5) If current does not flow to both terminals at the same
time, remove cap from throttle sensor adjusting screw and adjust
throttle sensor.
6) Adjust timing of current flow to voltmeter "A" in Fig. 2
by turning throttle sensor adjusting screw.
7) Turning screw in causes current to flow to Light
Green/Yellow wire at lower engine speed. After adjustment, install
cap on throttle sensor adjusting screw and retest throttle sensor.

SHUTTER SOLENOID VALVE

1) Disconnect vacuum sensing tubes from shutter solenoid
valve (Yellow color dot). Blow through solenoid valve through vacuum
hose "B" shown in Fig. 3; air should go through valve and escape at
front port.
2) Disconnect electrical connector and apply battery power
to terminals on solenoid valve. Blow through hose again; air should
escape through air filter at rear of solenoid valve. Replace valve if
it does not respond as outlined.

DECELERATION CONTROL SYSTEM

Article Text (p. 4)

1983 Mazda RX7

For www.iluvmyrx7.com

Sunday, August 26, 2001 04:58PM

Fig. 3: Testing Shutter Solenoid Valve

SHUTTER SOLENOID VALVE SIGNAL CHECK

1) Warm engine to normal operating temperature. Stop engine.
Connect tachometer to engine. Connect voltmeter to negative (Light
Green/Yellow) terminal of shutter solenoid valve electrical connector
without disconnecting connector.
2) Disconnect throttle sensor electrical connector
(Black/Yellow and Green/Black wires). Shift automatic transmission
into "P" or "N". Start engine and run at idle.
3) Voltmeter should read 0V at shutter solenoid valve
terminals. Disconnect electrical connector from throttle sensor.
Voltmeter should read near 12V and engine idle is erratic.
4) Shift automatic transmission into "D". Connect throttle
sensor connector disconnected in step 1). Voltmeter should read near
12V.

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