Mondeo 1997 keeps stuttering?

My !997 Ford Mondeo (1600 Zetec) keeps 'stuttering when accellerating. It doesnt always do it but when it happens the engine appears to suddenly arrest then recover and carry on. It fires on all four and idles very well too but it just has this rather puzzling intermittent 'stutter' (for want of a better word). Apart from this it is (or would be) a nice car to drive. Any ideas please?

Barry
July 2006