W140 3,2: Ice build up in intake ?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Jens - 02 Apr 2006 01:28 GMT

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 ?

Reply to this Message

James O'Riley - 02 Apr 2006 02:15 GMT

> 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
[quoted text clipped - 27 lines]
>
> Has anyone else experienced this, and if so what to do about it ?

Sounds like you have carbs and in that case you are exactly right. In
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.

Reply to this Message

Jens - 03 Apr 2006 07:07 GMT

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?

Reply to this Message

Jens - 21 Apr 2006 07:13 GMT

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.

Reply to this Message

Apple Dumpling - 02 Apr 2006 02:15 GMT

I have only had icing in an airplane with a carburetor at low manifold
pressure (low throttle). If you have a carburetor and are about idle
the rest of the conditions are right.

Bob

Reply to this Message