Dicky Speedo

[phil1234]

Hi all
Have just purchased a 1994 ssrx 3.0 and while the speedo is accurate (been converted to mph without actually replacing it by means of some chip or other) the needle seems to jump up and down whilst idling. That I can live with, but whenever it does so it also bumps up my mileage on the counter. How can I solve this irritating problem, any suggestions please?

[TonyN]

I'd pull the dash out and check all the plugs, plus the soldering on the chip itself, and also the plug on the t/case where the speedo sensor is.