Some things to check:

Timing (too much advance)
Fuel system--too lean.  Check pressure and injectors
Carbon build up can increase compression--try a gas additive designed to
burn carbon deposits, and you can switch to a higher grade of gas.
Cooling system problems can cause engine to run hotter than normal and
knock.

Also, don't lug the engine, downshift your A/T manually into a lower
gear when climbing hills.  Probably the lowest gear if you are only
doing 15 mph.

Unfortunately, it sounds to me that this engine needs a rebuild, it
should be able to pull faster than 15 mph on a grade when in the right
gear.

Justin Wolfe wrote:
>
> I am absolutely terrified to bring my van up long steep hills.  One is
> that I drop to about 15mph which maybe normal for  a auto transmission
> in a 84 westy, but what really scares me is the engine temp goes way up
> and the engine begins to knock furiously.  What the hell can I do?  I
> live in the green mountains of VT so I go up and down constantly.  I
> even have to plan trip routes to avoid areas where I know there is a
> steep long hill.
>
> Justin

--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Daily driver since 1969)
'74 MGB GT (Restoring sloooowly)

Personal mechanic for:
'70 MGB GT (Daughter's)

Assisting on Restoration (and spending OPM):
'72 MGB GT (Was daughter's, now son's)
'64 MGB (Son's)

Stripped and gone but their parts live on:
'68 MGB, '73 MGB, '67 MGB GT