I have a 2001 Daihatsu Cuore sport, recently it has started cutting out.

After the engine has warmed up and the car comes to a standstill ie lights, junctions etc, the revs are dropping to 0 and the engine cuts out. It will start straight away though.

A local garage has suggested a step up relay problem but after a google search I can't find anything about one of those.

Can anyone shed any light on what could be the problem?