Deceleration Valve Relay: Description and Operation

Fig. 30 Decel Relay Terminal ID:

The decel function shuts off the fuel supply when the accelerator is released at engine speeds above 1575 RPM and at engine temperatures above 113°F (45°C), or alternately, during a 140 second period after starting.
When the accelerator is released, grounding is done through terminal 1 in the throttle position sensor to terminal 30 on the decel relay, Fig. 30, thereby providing a signal from terminal 87 to the fuel shutoff valve. There is also a signal from terminal X1 to terminal 12 in the ECU, and a pulse ratio of 60% is selected to compensate for the leaner mixture sensed by the oxygen sensor.