We have a 2006 Ford Focus Zetec 1.8 TDCi Climate Pack, which we bought less than a week ago. After picking it up from the garage we bought it from, we noticed that there would be a loss of power when driving, mainly in 1st or 2nd gear. It has happened when pulling from a junction in 1st, and also when going uphill in 2nd. When the loss of power happens, if you take it out of gear and then put it back in, it seems ok. Although today, my wife was driving and she had to pull over, and leave it in idle, for a minute or so. There are no warning lights, and the engine doesn't cut out. We took it back to the garage we bought it from, and they had a look(as it is under warranty), and hooked it up to the diagnostic machine. No codes came up, and the guy who did the test said that it was one of the best engines he had seen, as all the readings etc were near perfect. The only thing that fluctuated a very tiny amount, was something to do with the air flow(?), but he said it should clear itself in a week or so. The garage told us to take the car away, and see how it goes, and if it played up to bring it back(we picked it up yesterday morning(Tuesday)), and since then it has happened again 4 times. When driving along the dual carriageway it has been fine, and the acceleration has been fine aswell. It only seems to be in the lower gears(1st and 2nd). Does anybody has any idea what it could be?

Sounds like mass airflow sensor.Unplug the electrical connector to it and drive it a bit and see if makes any difference...

Many thanks for that. How much would it cost to have this replaced, and is it something I could do myself, or is it a garage job?

If it is the sensor then expect to pay up to 100 quid or maybe more.Its easy to fit.But I would unplug the connector to the sensor first and drive for a bit just to see if it makes any difference.If you notice no loss of power then it is the sensor.You could try cleaning it with mafs cleaner first before you buy a new one its a hell of a lot cheaper that way..

Which part of the engine would I need to be looking at, as I know some basics, but am not that mechanically minded. Is it ok to drive for a while with it disconnected(as the fault doesn't happen all the time), or can i only drive it for a short distance?

Hopefully someone with a 1.8 will see this topic and help you further as not to clued up on 1.8's.It should be on the airfilter housing.Google it and look at the images to see if its the same as yours...Sorry I cant help you further..