StrobeWylan

So you have vacuum at the snorkel motor at all times?

Ok, winter has returned and I'm back to trying to solve this. I hooked up a vacuum pump to the snorkel motor and it operates the butterfly just fine. I do not detect any vacuum though on the line that goes to it. When should it have vacuum? Is it when engine warm, cold? Is it outside temp related? I'm confused though. The problem doesn't happen until I drive 10 miles at highway speed. It runs really good when the engine is cold. So if the warm air is used from the heat riser tubing only when engine is cold, how does it prevent carb icing when the engine is warmed up [which is when mine happens]? I'm wondering about the "The coolant lines at the base of the carb should keep it warm enough to prevent icing." as Gloyale mentioned. I see one line that comes from the thermostat and disappears under the carb somewhere. It's the size of a gas line hose. I don't see where it reappears on the other side or another return line. What am I looking for?

I'm not sure what the temp switch and the snorkle door motor are. Are they what switches the air supply to the heat from the exhaust?

Yea the tube is there. I swapped out a different air cleaner housing just in case it was not switching properly. TOday it rained and was about 50 temp. I took it out on the highway and it ran fine. So it does take the 30-40 degree temp plus moisture to get it to fade power. Like I said when the problem did occur I quickly opened the air cleaner but saw absolutely no icing inside.

My 1987 DL runs great except when we get rain/snow mix when temp is 30-40F. Happened yesterday and I quickly took off the air cleaner top to look for frosting in the carb. It looked really clear inside. I have 2 parts cars and have tried a coil I know is good, also a distrib. I looked at the distrib and it looked dry. I'll watch it though in case I missed something. The way this happens: It will run great. Then after about 10 minutes (only when theres a rain/snow mix) the power starts to fade. No backfiring. Just a fade of power that takes about 10 minutes til the engine quits. I pull over and wait about ten minutes and it will start up and run great for another 10 minutes. Then it starts to fade again. Actually we had been a climate where we did not get rain/snow mix except rarely. Now that seems to have changed. We used to get snow from Canada and it was a dry snow, took a foot of it to make an inch of water. It came with very cold temps. So this is a new experience for my SUBE. :-\ Any ideas??