It depends how bad it is.
The first ST I had was terrible and felt like a miss-fire.
The current ST has the problem but nowhere near as bad.
There is a miss-fire sensor on the engine so if it was a real fault it would put the light on.
They'll just tell you it's a charchteristic of the car.
Mention it though by all means.
What fuel are you using BTW?
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2011 Focus 3-door Zetec 1.6 TDCi.
Previous <img src="/images/graemlins/stemo.gif" alt="" />s - 2006 Panther Black & 2007 Red. Gone and quite forgotten <img src="/images/graemlins/lol.gif" alt="" />