W140 3,2: Ice build up in intake ?

:
When going to Copenhagen airport, the motorway ends at a roundoubout. So you drive at a speed of 110 km/h (70 mph), take the foot off the accellerator to slow down and finally stop at the roundabout, waiting
to get into it.
A year ago on a foggy/rainy day at a temperature at 5 C (40 F), I drove that way in the morning rush hour, and when stopping at the roundabout, the engine went out and couldn't be started.
Well, that wasn't funny, because there is only one lane into the roundabout, and I blocked that. Imagine the concert of horns behind me (and I was already in the last minute to catch the plane).
After some 10-15 minutes, it could be started, and the engine ran smoothly again. No problems since.
Until today. Exactly the same weather conditions and exactly the same roundabout. Fortunately, there was no cars in the roundabout, so I could roll aside. And I was not in a hurry this time. So I tried to start a couple of times while listening to some good music, and after 10 minutes I started and drove away.
An hour later on my way back, exactly the same happened at the exit of the motorway.
My theory is, that the sudden high vacuum in the intake causes some ice build up due to the very humid air and the relatively long time it takes to slow down, and the 10-15 minutes is the time needed to melt it.
Has anyone else experienced this, and if so what to do about it ?
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Jens wrote:

the early years (1960's) that would happen to VWs and Prosches. The carbs were separated from the manifolds by 1/2" aluminum for winter use, or phenolic for summer use. Don't know if you can do that or not.
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Well, if it was carburetor, I would not think twice, but this uses the LH-SFI injection system.
Still, when deccelerating from "high" speed, a relative large amount of humid air must pass through the narrow gap in the closed throttle.
So, has anyone seen such behavior, or should I look elsewhere?
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Problem solved.
It was not anything in the intake system, but the ignition coil.
Don't ask me why it would fail only when stopping after having driven fast on the motorway and not in other situations.
It was also misfiring above 5000 rpm (which I rarely drive), and that problem is also solved now.
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pressure (low throttle). If you have a carburetor and are about idle the rest of the conditions are right.
Bob
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