I have a Ford Focus, 2002, CL, 1400 petrol.

Actually, it's not mine but a friends and I just fitted a new battery. When I drove it I realised the accelerator seems to stick. When driving, slowing down by talking your foot off the pedal doesn't quite do it as the revs stay up around 1500/2000RPM for a short while before dropping to normal tickover. Easy to rear end someone!

Testing at standstill the revs still hang high and lifting the pedal makes no difference so it's not 'connected'. I'm assuming there's no mechanical cable to lubricate so what could it be?