Hey this is my mum account but i am using it, i too havea ford focus but i have a w plate ford focus estate 1.8tdi cl
my problem that happend last night three times and twice this morning is.
I'll be driving down the road at just over 2k rpm and then i will feel a small jerk (like no fuel briefly).
Then a few moment later the car will go to idle, drop out of gear(gearstick still in gear) and a flashing light on dash board will start to flash.

thanks for your time
ricky

p.s. i recently put a amp and new speakers in the car but i think this is going to be unralated but it is the only thing that i have changed about the car recently. and i did get it all checked by a audio person he said it was all good

you will have to get the fault codes read from the ecu,any good local garage will be able to do this for you,hopefully this will point towards what the problem is.

Could be a number of things, sympotms are similar to mine when the Fuel Filter went pop.