We have had this problem before in our family with both a 1996 Voyager and
a 1997 Caravan, both with the 3.3L engine. It first happened on the
Voyager when it was still under warranty. I had it in to several
different dealers before I found one that new the trick to fix it: Clean
the throttle body valve in the air intake system. Ever since the dealer
told me what they did, I've been doing it myself on both of our cars
periodically when the stalling comes back.
Just remove the plastic box that sits on top of the air filter box, and
remove the flexible air hose to the throttle body. Tiny bits of dirt and
gum that get past the air cleaner tends to
accumulate on the butterfly plate and the housing right where they meet
when the your foot is off the accelerator. It doesn't take very much dirt
to starve the engine of air, which causes the stalling. The dirt comes
off pretty well with carburetor cleaners, although I've found that rubbing
it off with a clean & dust-free cloth soaked with a little cleaner is much
more effective than just spraying. Wipe both sides and the edge of the
butterfly plate and the housing until you no longer see the dirt coming
off on the cloth. You may want to check that the cleaner is safe for the
oxygen sensor if you end up spraying some in.
This cures the stalling problem every time!