Question for you all.
My '81 Westy has been running superbly all through our recent cold snap, until this morning. When I went out this morning, it started up fine, but once in gear it ran poorly. In order to make any progress, I had to keep it in lower gears, and rev much higher than normal. After a few minutes, life returned to normal.

However, after about 20 minutes of driving, I shut down for a short while, and the problem returned upon starting again. I lost almost all power on _any_ hill, was getting regular backfiring, and finally had to park it and catch a ride.

There is a new sound coming from the rear of the van, perhaps engine area, don't think it's the gas heater fan, as it's turned off. It is not the rectifier/alternator, as I have recently repaired that, and am getting good voltage.

I'm stumped, and have checked the archives. I'm going to have it towed to our local gurus, but was wondering if any of you have an idea as to what may have caused this strange, sudden change in behaviour, from a previously perfectly running van.

Thanks for any advice,
Phil