if it is efi it may be the MAF. mass airflow sensor. if this is not functioning the ECU will not know the amount of air entering the engine there fore cannot give the correct fuel amount, in your case it could be playing up thinking your engine is at high revs past the limiter, where the fuel is then cut off, and as this happens and it is at low revs i could stall the engine.

but please, what escort is it? send a pic if poss.