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Vw golf 1.9tdi power loss

6903 Views 3 Replies 2 Participants Last post by  chittychittybangbang
Hi I am new to forums and not a technical when it comes to cars.
Please note the problem only occur when it has been raining.
I have a VW Golf 1.9TDI 2006 70,000 miles - well serviced, round trip of 48 miles to work on motorway and country lanes.
Several months ago it would lose power - limp mode BUT only when there had been heavy rain.
On one occasion this occurred at 65mph on the motorway - a great deal of road spray.
The power loss occurs at 30mph in 4th - drop to 3rd and rev up only to find loss of power.
The car has been into a VW dealer.
Salient points - the engine management light has never come on (except when first turning ignition key)
the diagnostic at the dealer shows no error codes. The dealer contacted VW Uk - the Ecu was cleaned up etc. Car satisfactory for a while bur problem re-occurred - result a new ECU (not cheap these things)
Again car ok for a while. Last week problem came back - recovery vehicle brought me home.
Took car out today - torrential rain - pulled into a car park and left engine running to warm it up. Slightly depressed the accelerator - up to 1500 revs - revs dropped back to idle. this occurred several times plus several times the revs did not increase at all even with depressing the pedal about half way. I am talking to the dealer tomorrow - but I know they are puzzled also - can anyone offer suggestions please - many thanks
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Here's one idea. It should have thrown a code but you never know.

The turbo vane actuator has an electrical sensor on it. The wires coming out of it often break. Carefully inspect the wire loom and expose the wire. Make sure that it's OK. Maybe water is splashing on it and cause the sensor to short out?

It's not the accelerator pedal - it should definitely throw a code.

Are your carpets wet? Maybe the rain is backing up due to clogged windshield drain or sunroof drain and leaking into the interior. If your windshield was replaced and they didn't seal it well water could also leak in. That could cause electrical components like the relay panel to short out or grounds to become corroded.
Hi many thanks for the reply.

The Turbo Vane actuator has been mentioned to me before - unfortunately I have no technical knowledge about cars. However it is something I can talk to the dealer about.
The TVA, should it only come into play at 2000 rpm to bring the turbo in or am I completely wrong -
I base this on a TDI car I had in the 1990's

I was losing revs while stationary at 1500 rpm

Please forgive my technical ignorance - your reply is appreciated.

The car inside is dry - no leaks etc.

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The actuator constantly moves at all times depending on engine rpm and requested turbo boost. Because of the fact that it only appears during heavy rain suggests that a ground is wet, a wire is rubbed through and getting wet, or water is corroding and shorting an electrical contact either inside or outside the car. There are so many sensors on the car that the best thing to do is to just look at all the plugs and grounds and see if you find anything. They should throw error codes but you never know. You might also find something like a broken vacuum line or loose hose clamp.
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