Mysterious speedometer and engine behaviour

[davidjaller]

Sometimes when driving the speedometer quickly goes down to zero and the engine gets noticeably weakened (at same moment). It stays so for some minutes then speedometer jumps up to correct speed and engine gets full power back, also simultanioulsy.
It doesn't lose power completely and its till fully drivable even if there is some slope, but it is clearly noticeable. It happens quite seldom, only on every 200 km's or so of driving, it has been occurring for a couple of years now without getting worse and with engine running fine otherwise. Engine light is not on. Its a 1.6 petrol from 2003.

Cant myself figure out what fault could make this symptom, and was curios if someone here has experiences something similar? 

Best regards
David, Sweden

[Sol]

Sounds like an electrical or ECU fault. I have heard of this before - it was an electrical issue. Cannot remember what the fix was. This may not be easy to track down. Mice chewed wiring in the engine fusebox or something.

[Kyleonsite]

I have a similar issue with mine, it tends to do it more in summer/warmer months, similar point on my regular commute to work, Speedo drops off to zero and in my case the engine performance increases!

The mileometer doesn't increase whilst the Speedo is stopped indicating it's the gearbox sensor but it only stops for a minute or so then starts working again.

I've extensively googled it and can find other occurrences but no information on how to fix it including asking on here