After about 2 miles it starts to misfire. This can be cleared briefly by depressing the clutch but then the misfire will return after a minute or so. The misfire also clears if when moving the ignition is turned off & on again & will not return so long as the car is cruising at a constant speed. The misfire returns upon accelerating after the gears have been changed down. The air flow meter has been replaced as well as the clutch switch. Its been checked on diagnostics & no fault showed up. Anyone any ideas.

My guess is HT leads or Coil Pack. When was the last time the HT leads were changed? These have a tendancy to break down once warm and the car is under load, such as in accellerating.

HT leads or coil pack.

Surely if the HT leads or coil pack were giving trouble it would show up on a diagnostics test?

firstly, which engine/model fiesta is it?

the early sigma (1.25 and 1.4 16v) engines had a common issue with the coilpacks going, luckily they are dead easy to replace (half an hour for a novice) and a cheap ish part (30 quid for a new one from a factors)

Surely if the HT leads or coil pack were giving trouble it would show up on a diagnostics test?

Not neccesarily, it's still a pretty 'dumb' component. A code would only be thrown if it caused a knock on effect.

Sorry I forgot to mention that it had the master cylinder replaced. There was no misfire before that.

The model is a 1997 1.3 Encore.

1.3 encore....lol....almost definitely going to be HT leads/sparks/coilpack

There are only like 3 other components on that particular engine.

misfires are generally down to ignition faults, i agree with dlockers, somewhere in your HT circuit.

just watch yourself on the voltages, they can give a nasty belt.