Deceleration Fuel Cut-Off

Deceleration fuel cut-off is a function of the ECU. When the throttle is closed, the reduced air flow through the air mass sensor causes the ECU the reduce the duty cycle to the fuel injectors, which reduces the amount of fuel injected. If the idle switch is closed and the engine speed is greater than a specified rpm, the ECU cuts the duty cycle to the injectors until either the idle switch is opened again, or the engine speed drops below the specified rpm, then fuel injection is resumed.