Just bought a P reg Escort 1.6 zetec, when i start it it revs up to around 2000-2500, then drops to around 500. It shudders but doesn't cut out and then goes way back up to around 2000 again and the process keeps going. after a bit of driving it seems to happen less frequently, but sometimes happens at traffic lights etc.

Anyone have any ideas or tips?

Cheers.

 

clean the idle control valve up, my mondy did the same thing, cleaned the icv up and it cured it.