1993 Opel Signum WHEN COMING TO A STOP

Engine problem
1993 Opel Signum 4 cyl Wheel Drive Type unknown Manual 100000 miles

MY QUESTION IS KIND OF BROAD, IT IS ON MY UNCLES 1993 OPEL, I AM NOT SURE WHAT MODEL OF OPEL IT IS, HE SAYS THAT WHEN HE IS COMING TO A STOP FROM AROUND 50-60MPH, THE TACHOMETER WILL SURGE SLIGHTLY, THERE ARE NO CHECK ENGINE LIGHTS ON OR LIGHTS ON THE DASH TO INDICATE SOMETHING. SO MY QUESTION IS CAN ANYBODY HELP NARROW THIS DOWN. I KNOW IT IS NOT THAT MUCH INFORMATION. IF I CAN GET ANY INOFRMATION FROM SOMEONE THAT WOULD BE GREATLY APPRECIATED, IF NOT THANK YOU FOR YOUR TIME.