If the tach dips or the needle jiggles say ...
my thinking would be drawn to the distributor.

I'd try a known good one  for a first step.
It's mandatory in my world to have at least a known good ECU and
distributor for self-rescue and testing.

Of the Hall Senders I have seen that have failed one way or another .....
it's been intermittent no-start cold,
or ....power loss, stumbling, and fialure to keep running steadily after
running a while.

I had two distributors in a row do that , 1.9 ones..
and each one took 3 hours of freeway driving before they acted up.
( happened at the same place on I-5 three  hrs north of where I am ..
  a year apart...exact same thing with two different used distributors,
same van. )

New Hall Sender fixed it.

It's nice to have another AFM too.
All I've seen those do is run 'unevenly' after many years. Subtle
unevenness ...
I did have one that would allow a 1/2 second cut-out at 60 mph, but that
was all.

Scott

On 11/14/2013 6:20 PM, Gregory Smith wrote:
> Heeeeeeeeelp!
>
> I am pulling my hair out trying to solve an ignition miss on my '88 GL.
> When it happens, the engine is warmed up and I'm usually just cruising
> along.  The engine stutters and the tach dips and even goes up a bit
> sometimes.  The fuel pump is good, quiet, filter is about 2 months old.
>
> Initially I suspected it needed and tune up and have replaced the plugs,
> cap, rotor, and wires using the appropriate parts from Bosch.  The
> problem persisted so I replaced the ignition switch with a new one.
>
> The problem persisted... reading up on the symptoms I thought it might
> be "vanagon syndrome" so I swapped in a different AFM, still there.
> Added the proper capacitor to the AFM innards, still there.  Unplugged
> the O2 sensor... still there.
>
> Any ideas?  Does the hall sender in the distributor do this when it's
> failing?  I think it's more of an on/off failure so I'm stumped.  Thanks
> in advance.
>
> Gregory Smith
> '88 Vanagon GL
> '77 Lancia Scorpion
> Olympia, WA
>
>