220d surging
 

I bought a 1969 220d that had been parked in a barn since 1981. We put a battery in it and it took right off running perfect and has run perfect until I started putting in new fuel. Now it lopes or surges when idling until its warmed up. Is this a timing issue with the new fuel being of a more refined quality because of emission ratings versus 25 years ago? Does the timing need to be changed?