oops, forgot about fuel!
Check your fuel filters, too. If they haven't been changed recently, change em. If the inline one looks black, you may have bugs (algae) in your tank, particularly if it has been sitting. Either drain and treat your tank, or fill it and treat it, change the filters and see what happens.
If you can, try using a fuel can as your tank, and see whether that helps. If the car runs with clean fuel from a can, you have tank issues.
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K