Deceleration Control System Mazda RX-7 FC

DESCRIPTION

Deceleration system is designed to maintain a balanced air/fuel mixture during deceleration and help prevent backfiring. System consists of a fuel-cut operation (non-turbo), throttle sensor, anti-afterburn valve, dashpot and air by-pass valve (turbo).

THROTTLE SENSOR

For complete testing and adjustment procedure, see ENGINE CONTROL SYSTEM article in the COMPUTERIZED ENGINE CONTROLS section.

ANTI-AFTERBURN VALVE

1. Operate engine to normal operating temperature. With engine idling, disconnect air control valve-to-air pump hose at air pump. Place finger over opening and note that air is not drawn into the air hose.
2. Accelerate engine above 3000 RPM and then rapidly decrease engine speed. Note that air is drawn into air hose for a few seconds during deceleration. Replace air control valve if anti-afterburn valve did not operate correctly.

Inspection

1. On turbo models, remove intercooler. On all models, fully open throttle valve. Push inward on dashpot rod. Note if rod slowly retracts into housing while pushing on rod.
2. Release rod and note that rod quickly extends. Replace dashpot if rod did not operate properly. On turbo models, reinstall intercooler.

Adjustment (Non-Turbo)

1. Install tachometer. Operate engine to normal operating temperature. With engine idling, increase engine speed to 3500 RPM. Gradually decrease engine speed.
2. Note engine speed at which dashpot rod contacts the throttle valve lever. Rod should contact lever at 2700-3100 RPM. If not within specification, loosen lock nut and turn dashpot to obtain correct reading.

Adjustment (Turbo)

1. Operate engine to normal operating temperature. Stop engine and remove intercooler. Disconnect throttle sensor connector.
2. Using ohmmeter, check resistance between terminals "A" and "B" of throttle sensor connector. (Scheme 26) Resistance should be 1800-3800 ohms when dashpot rod moves from throttle lever.
3. Loosen lock nut and adjust dashpot to obtain correct resistance reading. Reinstall throttle sensor connector and intercooler.

Scheme 26

Remove air by-pass valve. Connect vacuum pump to port "A". (Scheme 27) Apply 11.8 in. Hg vacuum. Check that air flows through port "B" and "C". Replace valve if necessary.

Scheme 27

FUEL-CUT SYSTEM (NON-TURBO)

Operate engine at 2000 RPM. Ensure engine speed varies when throttle sensor is pushed inward. DO NOT completely push throttle sensor inward.