My Saab900 2.5 V6 with the automatic transmission started "bucking" and the engine speed jumped up and down while trying to maintain a steady speed up a hill. That was in "D" with the rpms 2000 or under. If I "manually" shifted to 3 or 2 to keep the rpms above 2000, it was smooth.
Obvious I would like to think it is the distributor and not the transmission . . . If it is the transmission, the car is not being fixed.
Fortunately I also have a classic Saab 900 to drive :-) It's red box turbo time!!!