Vw golf loses power in the rain

[ARIMUS]

Car is a 2006 VW Golf 1.9 TDI - 70,000 miles - good service history.

Several weeks ago loss of power = limp mode, when we had heavy rain.
VW dealer could not find a diagnostic error code. Cleaned up the ECU which seemed to work for a while. Several weeks later problem occurred again - result a new ECU - ouch! Again seemed to solve the problem - even when raining. Today after heavy rain had to be brought home on a breakdown truck.
The car does not like wet weather - no rain runs like it should do - good acceleration etc. By the way daily work run is 24 miles both ways mainly motorway.
The new ECU does not give any error code, engine man light only comes on when ignition key is turned. I have tried turning the engine off and restarting - no effect.
By Limp mode car will not exceed 30 mph in 4th gear, if I change to 3rd I can get the revs up to 3k and accelerate but then the car decides to lose power.
Has anyone had such a problem - VW dealer is stumped. :1zhelp:

[phil miller]

hi mate, when i read the title first thing i thought was the ECU is getting wet, then i see its already been replaced so that keen of puts pay to that, it could be water ingress in the engine wiring loom, apart from that without looking at it nothing else seems apparent, it only does it in the rain so that makes me believe its something getting wet and shorting out, hope the dealer can sort this out for you bud

[Ben]

you also posted in the wrong section. Suggest you use copy and paste.