HarryST170 replied to Jacko9966's topic in Ford Focus ClubHi, I have a focus st170 and have the same problem but it's higher up the revs, anything above 4500rpm and the jerking stars. This problem started about 2 weeks ago and at the start of this week it got much worse. No power coming from anywhere and it was a pain to drive, jerking started at about 3000rpm this time. I changed the spark plugs but nothing changed so booked it in and the garage said it was the coil pack. Got it back Friday apparently it was 'running like a dream' at least by that statement i know nobody had been out taking it for a drive. So spark plugs and coil pack haven't worked for me!