Help Needed: Engine cutting out on 4kq

[Jpinkowish at aol.com]

Hi folks,
In the 125K miles I've put on this engine I have never had a starting or
running problem.  So, this is a first.

An archive search hasn't produced anything firm yet.

The patient is an '85 4ksq, 2.2L.

Here's what happens:
COLD START CUT OUT
--turn ignition to "on"(not crank), tach needle bounces to 1K and fuel pump
operates for 2 sec and then shuts off.  I don't recall ever seeing this tach
bounce before.
--crank engine; starts right up.  Idle starts at 1200-1300 rpm(outside temp
of 65degF) and is smooth.
--after about 2 mins at idle car stumbles very briefly, then instantly stops.
 Fuel pump continues to run until just after engine stops.
--wait about 1 min, turn iginition to "on", same tach bounce/fuel pump
operation.
--crank engine, car starts right up, idles smoothly, warms up to temp fine.
Normal temp and idle.  Fuel pump runs quietly.
--drive car to highway, drive on highway, drive on local roads to
destination.  Car pulls strongly, idles smoothly, no cut outs.

WARM CUT OUT
--4 hours later, start car, idles smoothly, warms up to temp w/out incident.
--drive on highway, car pulls strongly, runs smoothly.
--exit highway, shift into neutral to cruise to exit end, RPM gets to
1000-12000 and immediately drops to zero.  No stumble, no run-on; all the
idiot lights come on.
--wait 2 minutes.  Turn ignition to "on", get same tach bounce/fuel pump 2
sec buzz stop.  Engine requires 3-4 sec of cranking to start, stumbles for a
second, and then runs smoothly.
--I finish drive home on local roads at 30-50mph by keeping RPM above 2000
--Pull into driveway, let car idle for 5 min, no stumble, no cut out.
Wiggling wires, the intake boot, and vacuum hoses produces nothing.

The "warm cut-out" scenario repeated 2 days in a row.

Supporting info:
--all battery, alternator, and ground connections are clean and tight
--alternator has about 70k miles on it
--fuel pump and fuel pump relay both have about 60k miles
--fuel pump prefilter has about 60k miles, filter just after fuel pump has
about 30k
--branded fuel, repeatedly from same station
--ICV hums/vibrate
--fuel pump does not stop until after engine stops(during the cold start
stall anyway)
--coil resistance checks out OK

I'm trying to understand what electrical/mechanical phenomenon would cause
this stalling at low RPM, disappear after a restart, then reappear after a
highway run, then disappear again so that I can idle in the driveway for 5
minutes with no problems.

Things that come to mind:
--an electrical intermittent that causes a sudden loss of fuel pressure that
appears at low RPM.  I don't understand how this electrical intermittent
corrects itself.
--flaky fuel pump relay
--flaky fuel pump
--something in the distributor????

I need some help on this one.

Jan Pinkowish
'85 4ksq
Bristol, CT