99 Ford Focus Diesel - engine revvs down upon accelerating

1999 British-registered Ford Focus Diesel
124000 miles

I've just purchased this car used from colleague whom I trust. Lately though, as I'm driving, accelerating in second, third or fourth gear, the engine just revvs back down to idle for now apparent reason. At the same time, the glow plug light indicator (the one with the filament coil) flashes. No other lights come on (not even the engine management light). No strange noises are heard. The only cure to this is to simply swith the engine off and back on again. Sometimes the problem happens every 3 minutes, but I've also gone 80 miles without anything happening all day.

I've taken the car to a mechanic. They've done a diagnostic scan but have found nothing. They admit there's a problem as they drove the car and experienced the fault themselves. They now recommend that I take the car to a Ford dealer here in England. I'll do that but it's quite expensive so I was wondering whether someone might have an idea of what the problem is.

Thanks.

 

the glow plug light on the focus diesel is the engine management light. could be so many possible faults it would be best to take it to a ford dealer, or an independant with wds2000 or IDS diagnostic equipment as these are the only systems which will properly check out the management system on this vehicle. most other systems only read codes.