Annoying cut-out issue

[clearspark]

Hi there, I'm having an incredibly frustrating issue with my 1991 petrol 1.8 automatic golf (123,000km). It started about 6 months ago when I was on a long journey - the engine completely cut off out of the blue. The rev gauge immediately went to zero and the oil light came on (even though I was still doing 100km/h and it was in gear). I pulled over and tried to start the car. The engine turned over fine (i.e. battery was fine) but it didn't sound like it had any chance of starting - like it had either no fuel or no spark. I left it 5 minutes and tried again - no joy. Then not knowing anything about engines, I wiggled some wires and tried again - no joy. 5 minutes later tried again and it started perfectly like nothing had happened.

Since then it has happened a few times - both on long 5 hour journeys, and 5 minute short ones. There doesn't seem to be a correlation to humidity or engine temperature. Annoyingly, you have to leave the car for a few hours now or overnight before it starts again, but when it does start, it's like it never had a problem. It either works perfectly or not at all. The strange thing is though, that if you leave it overnight, guaranteed it will start first time perfectly.

I put it in for a tune up about a month ago and the engine sounds a lot smoother. They changed all of the filters and plugs and fitted a new distibuter cap. The problem went away for a full month but it has happened twice in the last two days now. Both times were in dry weather and occurred about 25 minutes into a journey.

The grounding wires to the engine block look slightly corroded, but I've tried wiggling them as someone turned over the engine and it didn't help.

I read a few similar stories about this problem that narrowed it down to a signal from the MAF sensor, but I tried the fix for that and still no joy.

Any help would be more than appreciated.

New distributer? Change a sensor? ECU? Electrical grounding? Fuel pump?

Anyone have any ideas?

Thanks,
Andy.