My 87 has had this problem for several months now, but becomes more apparent as the weather gets cooler.  Van starts fine, but immediately dies.  If you start it, hold down the accelerator to keep rpms up for a minute or so, it will then idle fine.  (Tuned up back in May, passed smog fine.)  What would cause this?

> Thanks for your help.
> 
Donna, 1987 & 1990 Vanagons