sudden engine misfire and self cure

[cureton]

Strange one this. While driving, suddenly engine shows kind of misfire, still runs and idles but feels and sounds like running on 4 cylinders only. Stopped, switched off engine, started engine and everythings fine again. Happend twice now, once while stopping at a traffic light, second while driving along country road. Changed ignition coil as it looked a bit dodgy (black stuff leaking out)Thought problem cured but came back while driving on motorway. Drove off to car park, switched engine off, back on and fine. Any ideas where to take a deeper look? Many thanks in advance!

[cureton]

Trouble is I cannot reproduce the fault, so I'll just have to wait until its happening again. Will check ECU connection in the meantime. ECUmate is on order now as it seems sensible to leave it plugged in for the case. Might well be a problem with the road speed signal telling the ecu to switch into idle mode when car is still moving. But then, would the car not properly idle when stationary? I think mine doesn't. Keep you posted.

[cureton]

Update from my side as I started the thread. Finally got the ecumate, nice piece of equipment and interesting to play with. Told me Fault 68 road speed sensor or wiring. No other fault codes thrown up. So will look at the speed sensor (have T5 gearbox)maybe dirty or misaligned, will also check cables.
If i can't find anything could it be the signal converter behind the dash? And if so, is there any replacement or spare part available?

[cureton]

I finally got the car on a ramp and decided to start checking from speed sensor at diff side. Sits in front/above of diff, bit fiddly to get at. Two wires attached to it, one was hanging loose just touching the contact. Easy fix, hope that cured the fault.