RE: Flat spot when accelerating from a stop with warm engine
I'm following this thread with a lot of attention since I've been dealing
with/just dealt with the identical problem with the 2.1L in my '90.
Had been running fine for several years.  Last December, just before a long
trip and while having a bunch of other routine maintenance done I asked my
mechanic to check the timing, not looked at for a long time.  He checked it
and tweaked it, said it was just a little off spec.  But driving away from
the shop I found that full throttle acceleration from a stop, after warm up,
was flat.  Didn't stall or die, just flat until about 2,000 RPM.  Lived with
it for the trip.  And one of the most knowledgeable Vanagon people I know
checked everything out when I stopped by his place during the trip and
couldn't find anything.  When I got home I got together with my mechanic
again and we tackeled the problem.  Ended up advancing the timing to about
10 degrees and that cured it about 90%.  But could find nothing else. Whats
been said here leads me to want to try the spare (and virtually new) AFM I
have.  The current AFM developed 'Vanagon Syndrome' about a year ago (cured
with the factory pig tail) so I'm wondering if the problem lies there.  BTW,
155,000 on the van and still the original engine.  Gas mileage is where I
expect it, 18-19 on the highway, and runs great otherwise.