Abstract: Resilient means yieldably opposes opening of the throttle for an automobile engine when the latter is accelerated too rapidly for acceptable fuel economy. Pressure actuated means responsive to inlet manifold pressure withdraws the resilient means from the path of opening movement of the throttle to enable throttle opening without opposition by the resilient means when the rate of acceleration is sufficiently low to achieve the acceptable fuel economy. The throttle opposing force of the resilient means is readily detectable by the automobile driver, but may be overcome by him when rapid acceleration is desired. Also supplemental means under the control of the driver is provided for selectively withdrawing the resilient means from the path of throttle opening movement when no indication of rapid acceleration is desired.