Having a big problem with my Fiesta mk6 tdci at the moment. 

Symptoms

• Car loses all power suddenly and cuts out. (Then have to turn the ignition to start the car again)
• Battery light flickers on and off when it is being driven.
• Steering wheel locks up due to no power when the car cuts out. 
• In recent weeks the car has cut out a few times when being reveresed and has been a litle bit sluggish going up hills. (This was happening before the car was cutting out all the time and losing power)

Other info

• Car still starts 
• Tested voltage of the battery and alternator and they are fine. 
• Cleaned up sensors and battery connectors. 
• Removed negative battery connector and the car still run but was stuttering a bit. Then turned the lights on and the car stalled. 
• Checked MAF sensor (Clean as a whistle) 
• Green flag looked for error codes and no codes where found. 

I have ruled out the EGR valve because in my opinion it is an electrical problem because of the symptoms. 

I haven't taken the car to a garage yet as I am trying to find the problem myself first. 

Any thoughts and suggestions would be much appreciated. 

 

 

• "Battery light flickers on and off when it is being driven."  what kind of rpm do you mean when the battery light is flickering? is the alternator drive belt and tension good?
• "Tested voltage of the battery and alternator and they are fine. " what voltage was it showing across battery terminals when revving at say 2000rpm?
• "Removed negative battery connector and the car still run but was stuttering a bit. Then turned the lights on and the car stalled." I have always been told that running it with no battery connected can damage the voltage regulator/rectifier built into the alternator, I don't know if true or an old wives tale, but I have never risked it.  

 

I am not 100% convinced it is electrical, I am not saying it is not, but based on experience I am wondering if it is a fuel filter problem. how many miles since it was changed\?

Fuel filter changed less than a thousand miles ago. 

Car only seems to cut out completely at low speed, When at a higher speed between 50 - 70 mph,(Roughly 2000 - 2500 rpm) it miss fires really bad then looses power then all of a sudden gets power back abruptly.  

When the engine was turned off battery was showing at 12.69 V and when the engine was running alternator was showing 14.20 V . Put foot on the accelerator and the voltage did not go down or spike really high. (Also turned lights, heating, ect... on,  no change in alternator output. 

Battery light not on all the time. On one occasion when it was really bad the battery light stayed on for about 5 - 10 minutes at a speed of 60 - 70 mph. Then intermittent other times. The battery light does not stay on all the time. 

The car starts fine at the moment but can't drive it at the moment because of this problem. 

Might be worth swapping out the alternator (for an assumed-working used part if need be) in case the tests performed have not picked up on it being faulty.

I’ve got exactly the same problem. Had new battery and alternator installed and it got worse. Still getting worse.