Alfa 75 sensor problem
i own a 1990 75 t.spark. the speedometer has a weird problem. it will read speed fine for a while while driving but then suddenly the needle shoots off the chart (over 240 km/h) and the mileage starts clocking over like crazy because it thinks the speed is so high. Then when you press the trip meter button on the speedometer, the needle will drop to its original postion, that is until the accelerator is hit once again, then it jumps off scale again.
I was wondering if anyone would have any ideas at all on what this is and more importantly how i can fix it as it is quite annoying. I'm guessing it would either have to be something in either the actual speed sensor or something in the alfa control which i hear is notorious for mishaps.
any help would be greatly appreciated