Ok I may have posted on this before but its still not resolved.

It only happens with colder outside temperatures, and I think only if the van has been in the cold for a number of days w/out being driven (I don't drive it on a daily basis).

Cold start with 40F or below outside temperatures and it starts and idles fine, and initially drives fine. But then sometime during warmup (2-10 minutes after starting to drive) the problem occurs, then goes away after warmup.

The problem is losing power when letting out the clutch either starting from 1st gear or shifting between 1st and 2nd or 2nd and 3rd. It is as if I am trying to pull a very heavy load and have to give it 5X more gas than normal to keep it from stalling between gears. Still runs fine at idle at any rpm not under load, during this period. I think it also tries to stall out at a higher RPM than normal during driving in any particular gear (i.e need to keep it above 2500 RPM).

I grounded the temperature sensor to help with hot soak restart, a year and a half ago, but I think I have had this problem for two winters going on three. I guess I could put this back to stock since I have since really fixed the hot soak problem with an aux. fan

Initially I thought it might be some mechanical drag on the engine when its cold, such as a sticky pwr steering pulley or such (mine was making some noise but I loosened up the belt and its better). But since it doesn't happen until after having driven for a few minutes it seems more likely to be something with the way the engine is running at a certain point in warm up?

Its due for a tune-up pretty soon, guess I should probably see if that helps.

Any other ideas? Fuel pump? not getting enough gas?