Look for loose wires, bad connections or most likely a bad sensor in the distributor. A broken connector on the dizzy can also cause the wires inside to get damaged. A bad ECU can also cause similar symptoms. The tach dipping/jumping indicates the problem is on the low voltage side so all those tune up parts were not needed. Vanagon syndrome has nothing to do with ignition. The airflow meter doesn't either. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Gregory Smith
Sent: Thursday, November 14, 2013 9:21 PM
To: vanagon@GERRY.VANAGON.COM
Subject: '88 GL intermittent ignition miss

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