Ruckle, then emergency program

Hello V8 expert,
my 89er 3,6l has the following new Macke: During the ride, without notice, he takes back the drivage completely with constant drive, as soon as I take back the accelerator pedal a tinyness (not to drive on the front man), the current consumption indicator goes to 0.0 - I give again minimal gas it pulls off clearly. So it goes about 5 km (where it runs normally in the stationary gas) then it apparently drives normally, but only in the third driving stage and can no longer be influenced by the selector lever.
Who knows advice ????