During closed throttle deceleration periods from higher engine speeds, fuel delivery is not necessary. In fact, deceleration emissions and fuel economy are adversely affected if fuel is delivered during deceleration.
To prevent excessive decel emissions and improve fuel economy, the ECU stops injection pulses completely during certain deceleration conditions.
• When the IDL contacts close with engine rpm above a given speed, the ECU cuts injection operation completely.
• When the engine falls below the threshold rpm, or when the throttle is opened, fuel injection is resumed.
Referring to the graph, fuel cutoff and resumption speeds are variable, depending on coolant temperature, A/C clutch status, and SIT signal.
• With A/C clutch on, fuel cutoff and resumption speeds will be increased.
• With the stop light switch on, fuel cutoff and resumption speeds will be decreased (some applications only).
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