My mrs has an A4 Avant 130tdi on a 51 plate, and for as long as we have had it it has had a running problem when it gets wet, or really damp. It will only do it when it is damp or wet, but by no means does it always do it when damp/wet......with me so far?! Then I shall continue!
IT manifests itself as having no power, you can put your foot to the floor in neutral sat on the drive and it'll struggle up the rev range. When out on the road it'll cut out a good few times. Its hard to get the damn thing moving along with the traffic, but it you keep you foot to the floor, when it eventually hits 3000rpm or so it suddenly takes off like a rocket.
While its doing this, the bit where it'll hardly keep up speed, it making a very rattly diesel noise, like a normal diesel rattle but turned up to 11, with a higher pitch, and black smoke pours from the exhaust. (Good innit)!
It wont do it if youve set out in the dry and it starts raining, so its not coming in through the grille, it only does it when its sat in the wet, so my thoughts its getting something wet down the bulkhead? Had a good root around, near the ECU and stuff but all seems dry.
Any ideas folks?