My friend has a 2001 1.3 Fiesta (endura engine) which has developed a cough under load.
She said it was due a service, so we did a full service including plugs and leads, which helped a little, however the judder/cough is still there. It only happens when trying to pull away from say a round-a-bout situation and trying to get upto speed on say a dual carrigeway, though intriguingly when up to speed it seems to drive as normal. It doesnt seem to be using anymore fuel than usual and the engine idles fine.

Anyone have any ideas what it could be?

 

Have a look at the coil pack, there prone to failing under load

 

Ill give it a go, thank you.