Does anyone have experience of this problem, my mechanic cant work it out.

Car starts well, drives 4 miles to the motor way well, goes for about 20 minutes on motorway well, then when I exit motorway and drive in lower revs, say, approaching traffic lights it wants to die. Sometimes it picks the revs up again automatically, other times it dies. When I try to restart it takes ages but eventually starts and I can drive it on.

The car has just had a full service after which the problem started. Have tried differend plugs. Have had the temperature sensor at base of radiator changed.

If you can shed any light on this I would be extremely grateful.

Many thanks,

Jimmy