Hi,

I bought a 2nd hand Ford Focus, its a 63 reg 1.0 Ecoboost (yes, I know, I've lost track of the number of people who've told me that's a notoriously bad engine after I bought it). It's slightly over 100,000 miles and no the timing belt hadn't been replaced, but it has now.

After like a week the head gasket blew going down the motorway after all of the coolant leaked out. Apparently a common problem on this model.

I bought it from a dealer, it was under their warranty and they rebuilt the engine, with a new head (they sent the old one to be skimmed, but that was unsuccessful for some technical reason). (they also replaced the timing belt at this point)

Anyway, so I have it back and it seems to be running very smoothly at speed, but there is a problem at idle. To me the engine feels like it's stuttering. When I tried to show the mechanic he said it was "misfiring slightly". Unfortunately, it's intermittent and one of those problems that goes away when you're trying to demonstrate it to a mechanic... So they haven't seen it when it's "bad", just maybe half stuttering.

It doesn't seem to make any difference when the engine is hot or cold. For example last night I got in the car after it had been sitting in the drive all day, I turned the engine on it was fine and while I'm sitting there trying to find something to listen to on my phone it starts stuttering - noticeably but not much - so that was in the space of about 30 seconds.

Where-as the day before I drove up the motorway a few miles, come off at the slip road and have to wait at the lights. While I'm waiting at the lights the engine starts to stutter again, almost to the point where it feels like it might stall.

To be fair it is most noticeable at traffic lights. ie. when I'm driving and then stop and stay stopped for a short time.

I did also notice a few times where there seemed to be no power in 2nd gear for a few seconds - ie, a residential road, slowed for a right angled corner, dropped to 2nd, and when I pressed the accelerator coming out of the bend there was no acceleration - I literally pushed the pedal to the floor and back and nothing (not even revving), then it just kind of kicked in after a couple of seconds. Possibly related, or possibly just my driving - I've had so many different courtesy cars in the last month it's ridiculous and they all drive differently.

Any thoughts on what the problem might be?