Bora TDI 2004 - surging / intermittent power loss

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

With the undertray missing, the crank speed sender is going to get very wet and it is not designed for it.

Thanks, I think I need to find an undertray and take it from there... ��

If it is all missing you can be looking at £500 all new and some of the side covers are now obsolete mainstream and only available from VW classic and there are nine different lefts and fourteen different right, at least there is only one Diesel centre cover as long as it is not the ARL PD150 or an auto

I let it dry out but the fault is still there... speeding up and slowing down on a steady throttle, but not like a misfire I don't think. I've done the injector harness before and it's different to that.

Maybe I need to get it plugged into diagnostics, not sure if it'll be something that throws up a fault though.

I had it in for a wheel bearing last week, and this is the second fault it's had since then. Clutch pedal feels dead although it's working fine. Anyway, one problem at a time...