I have a 2014 MK3 Focus which until recently has been runing a dream, two weeks back when i was heading home doing arround 70mph my car sudently dropped speed and power going from 70 to 50 ect, no matter if i dropped gear or not, I sank the accelerator but nothing, I then pulled over pushed the start/stop waited a minute then started up again and it was fine for about 30 minutes, and the same again, sine then it has happened another two times but it only seems to be when i am doing 60/70mph and only after arround 15/20 minutes, would anyone have any ideas before i go getting told a pile of **** from the garage 😛 thanks in advance. 

The sudden drop in speed from 70 to 50 is almost certainly the car going in to limp mode. Stopping and restarting can often reset it for awhile.

You need to get a laptop and download FORScan (it's free) and a connection lead vLinker FS (£40). You will then be able to connect to the cars OBDII port and check for any DTC's which may well be stored.

If there are quite a few (which is often the case) then make a note of them before clearing all DTC's. Drive about as normal and the next time the problem happens recheck for new DTC's this will give you a very good idea of what the cause of the problem is.

Download FORScan:  https://forscan.org/download.html

vLinker FS cable:  https://www.aliexpress.com/item/1005003116796694.html

OR

vLinker FS cable:  https://www.bmdiag.co.uk/forscan-diagnostic-cable-for-ford-vgate-vlinker-fs

48 minutes ago, unofix said:

The sudden drop in speed from 70 to 50 is almost certainly the car going in to limp mode. Stopping and restarting can often reset it for awhile.

You need to get a laptop and download FORScan (it's free) and a connection lead vLinker FS (£40). You will then be able to connect to the cars OBDII port and check for any DTC's which may well be stored.

If there are quite a few (which is often the case) then make a note of them before clearing all DTC's. Drive about as normal and the next time the problem happens recheck for new DTC's this will give you a very good idea of what the cause of the problem is.

Download FORScan:  https://forscan.org/download.html

vLinker FS cable:  https://www.aliexpress.com/item/1005003116796694.html

OR

vLinker FS cable:  https://www.bmdiag.co.uk/forscan-diagnostic-cable-for-ford-vgate-vlinker-fs

Hi Unofix,

Thanks for the advice, i will look into that however im not mechanically minded and therefore i wouldnt know what i am looking at on the laptop, it may be a coincidnece but i have noticed an issue with my coolant as well where the coolant disapears but my engine temp does not overheat and when i open the cap up to top up, the coolant rushes back into the container? could this perhaps be the issue which will require a garage check?

What engine do you have ?

This could be the early stages of head gasket leaking.

I have a 1.6 Diesel 

I'd buy a hydrocarbon test kit and check the coolant.

Thanks for both pieces of advice which I will look into 👍🏻