Juddering,clunking and warning light on

[Leesakk]

Hi,

Can anyone offer any help please?

07 1.4 tdci fiesta.

Car has been juddering for a couple of weeks when I acculerate and makes a clumping tingle kind of noise for about 3  seconds. It got a little worse couple of days ago and the cog light ( with an ! mark kept flashing ) I realised it has only happened since I put supermarket fuel in it.

Was told to fill up with BP or simular and add some cleaner to tank. Did this yesterday and car has got worse.

Was juddering more, lots of black smoke then light came on and stayed on with engine management problem. It then went into limp mode.

Managed to get it home and called the AA. It is showing a fuel flow problem and I was told not to drive it by the AA as he thinks it has an injector problem.  A friend of a friend of a friend came over and checked injectors and said it isnt them. He says it is more likely from the supermarket fuel and to run the tank down a bit, add more cleaner and fuel and take it for a drive. Did this this morning and it felt ok. Went out just now and it started playing up again with the same problems of jerking, making a noise, black smoke, light on and in limp mode.

Been told now to change fuel fillter and sensor but does anyone think that is what it could be as AA guy is certain it is an injector even though the friend of a friend of a friend checked and said injectors are ok.

Sorry for the long eassy. I have only had the car a few weeks and it ran fine when I bought it.

Thanks in advance.

Lisa