revs while idling

[shrimperwrx]

car starts fine and when running normally around 3500 rpm the engine goes back to idle fine , but if taking it above 4000 rpm the engine then starts to idle at around 1600 rpm. as soon as i turn the engine off then back on again it sorts its self out and idles fine !!! any theories...cheers

[MAXIBOY]

yes sounds like the road speed sensor on the speedo cable. make sure its earthed properly.