Hi

Driving home on the M4 last night in persistent rain, the car suddenly started slowing down/speeding up at frequency of about a cycle every couple of seconds. Coming off the motorway it didn't cut out or anything, and was idling fine. I got home OK although it continued to surge.

My initial thought was that water had got in somewhere and was intermittently shorting out the electrics for the injection (the car has no engine undertray) - does this sound plausible? Or possibly it's something to do with the control for the turbo, as each period of slowing seems to be preceded by a 'rushing' sound - fffffffffffff.

I'm going to use my T5 tomorrow instead, and see if the fault occurs when everything has dried out, but I'd be interested to hear any suggestions.

Many thanks, Andy