Hi folks. My daughters Focus is only managing 49mpg on a 100 mile round trip consisting mostly of motorway cruising. I've read fault codes and all 4 injectors are showing that they are exceeding their maximum learning limits. Can all 4 really have failed ir can their be another underlying fault? 90000 miles. Fuel filter was replaced at 60000. 

Many thanks.

 

The injectors haven't failed.  They've just worn beyond ECU correction possibilities.  Pretty much every 8v 1.6 TDCI has at least one injector in this state, mine had 2 by 6 years/42k miles.  I'm not at all surprised they're all worn by 12 years old.  They will need replacing if that's the case, though you can just put up with them until they fail MOT if you like.  It is probably about due another fuel filter now but that's unlikely to trigger these fault codes.

Thanks for the feedback Tom. I understood they wear out beyond correctable tolerance (a poor choice of words by me to describe them as failed) . I suppose I was just hoping that there may also be another underlying cause that could explain why all 4 are now in this state. I guess I'll just have to accept the inevitable and decide if the improved mpg is worth the not inconsiderable cost of replacing them all. I wonder what kind of improvement I might expect on like for like journeys?

1 hour ago, Bargain Bucket said:

I wonder what kind of improvement I might expect on like for like journeys?

I never did any long journeys in mine.  But averaged 55-60mpg per tank with two worn injectors.  If cruising speed is 70mph in 6th I would expect at least 60mpg.  Though if it's 80 or 90mph the MPG really drops off.  Odd as the Mk3 was specifically designed with aerodynamics in mind.

Does it warm up slowly?  You may get a better MPG improvement by replacing the thermostat if so.

Warms up nice and quickly (for a diesel). The front shutter works as it should too so I'm struggling to find any other reason for the relatively poor fuel economy other than the injectors.