For several weeks now my recently purchased 87 Gl hauler has had an
aggravating tendency to idle low or die when first started on a cold
morning.  It also would die at every stop sign for the first few
minutes. As the weather cooled more this got worse and finally it would
not start cold at all unless I held the pedal down a little while
cranking and then I had to hold the revs up for a minute before I could
drive away or it would die.

I tried replacing the plugs, cap, rotor and wires since all were
suspect. No change. I ordered a temp 2 sensor but before it arrived I
connected my Digitool and saw that the readings of that sensor were fine.

I left the Digitool connected and used the van daily while scratching my
head for what to do next. One morning I happened to have the Digitool
set to "battery voltage" and that gave me the clue I needed, as I
struggled to get it to start. I saw that the voltage was a little low
before starting the engine, dropping much lower while cranking. I opened
the battery compartment and looked for the date code on the clean
looking battery. There was a small sticker saying D01, meaning April
2001. 6+ years old. The terminal connections were clean and tight. I had
a newish spare battery, 1 year old, so I quickly swapped it in. The cold
engine started immediately and idled fine. It has continued to do so
ever since. No more stalling, period.

I never expected this to be so simple as a battery problem, since the
engine cranked fine. It was not until I had the Digitool hooked up that
I could see the problem. The Digitool has a setting where it displays
the voltage that powers the ECU, measured right inside the ECU. This was
showing 13.4 while the engine was running but only 11.xx when the key
was on but engine not started. During cranking it dropped to 9.xx.

Perhaps this is a case of a fresh battery masking some additional
underlying fault or overcoming a general weakness in the power supply
circuit for the ECU. The dieing behavior when coming to a stop while
cold was very abrupt,as though the key was turned off.

Mark