1986 2.1 2WD

I just swapped my engine for my spare engine (old engine had
blown head gasket).  Starts great, idles great.  Only one
problem.  Once the engine is up to operating temperature, it
stumbles and hesitates.  It behaves like it has water in the
fuel.  To not overlook the obvious, I added methyl hydrate
to the gas, but it's still behaving the same way.

Basically, you step on the gas, and it just feels like the
engine doesn't catch.  Then suddenly, it will catch for a
few seconds, then hesitate again.  The engine sort of
"stutters".  Idles fine.

The thing that bugs me is that it runs GREAT when cold.
When I swapped the engines, I replaced the Temp II sender,
thermostat, upper and lower thermostat housings, coolant
tee, rear main seal, clutch.  I have tried un plugging the
ISV to no avail.  Checked to make sure I connect the engine
ground strap.  Turn off the van, re-start, no help.  Nuttin.

Any thoughts?
Keith Adams | calgary.ab.ca
http://www.clubveedub.com
86 Westy | 59 Euro Beetle | 66 Beetle