If you remove pressure from the accelerator when the transmission wants to shift sometimes there is a loss of acceleration and the vehicle will start slowing down with the engine running with no engine warning light coming on. this intermittent problem has happened when the transmission shifts at approx. 2, 9, 19, 25, 40, 55 and 62 mph. when this happens the accelerator becomes disabled, the vehicle starts to slow. tapping the brake will slow the vehicle faster and the accelerator is ok/enabled.