Iddling

Got a weird scenario, when im driving the car and come at a stop the iddling remains above the 10 mark and seems to be revving higher than normal, then after a bit it goes below the 10 as it supposed too, any idea what would cause this and whats the fix?

tks
james

Dodgy earth to the road speed sensor is a common culprit for that, back of the clocks on the speedo cable itself, follow the wires coming off it & 1 of them will be earthed somewhere, just needs to be re-earthed properly so to speak