engine speed wavers during motion
I have a problem with my ’86 SL560. The car is fine when sitting still at idle, but if I take my foot of the gas when moving at 30-40 mph (going down a hill for instance), I have noticed that the tach needle wavers and you can fell the engine slowing and surging, maybe by +/- 300 rpm.
Any suggestions? The car only has 65K on the clock but wasn’t been fully serviced by the previous owner.
Thanks for any help,