Audi: stalling engine & strange behaviour

Hello all,

I just want to share some problem about my audi 80. I know what is causing
the problem...
It is about an Audi 80CD from '82 with a 5 cylinder carb engine.

The story: (and my apology about my English

It started some weeks ago that the engine suddenly stalled when I pressed
the clutch. The engine was just hot at that moment (green 'cold' light was
off). I was surprised about because it is difficult to stall this engine...
I thought it was because of my driving style and too quickly with pressing
the pedal when the engine was cold. However I never had this problem before.

Today I drove 700km with this car mostly on a highway, in rainy, snowy and
cold (below zero) weather. In the begin the engine was heated up well and
then suddenly infront of a traffic light the engine died. It also just
restarted like nothing happened.

When it was suddenly raining much and quite cold (around 0c) the engine
started to misfire irregularly when going 130km/h. The engine it self was on
normal temperature.

I stopped at a parking (engine died again) and looked under the bonnet. Took
off the air filter and saw something amazing... The carb holes were filled
with ice !! No wonder that the engine didn't went well.

Shortly after that I found the problem. There are 2 air intakes, cold from
outside and a hot intake coming from the exhaust manifold. There is a valve
between those two and some vacuum temperature switch inside the air filter
housing driving that valve. With a running engine and freezing cold outside
it was clearly that the air intake valve didn't work at all (all time at
cold air). I connected the 2 vacuum hoses together that were connected to
the air temperature switch and started the engine. The valve worked, it
opened so only hot air goes into the carb. I thought that's nice, putted
back the filter housing and went further with the car.
The 200km after that it went prefect, no strange shaking or stalling infront
of traffic light.

Now it is clear that I've to order a part at an Audi garage next monday .

Al