One more data point...

My 86 syncro had the same problem once.  I didn't do anything to fix it
but it hasn't returned.  This was at the end of an 8 hour drive right
after a stop for fuel.  To me, it felt like there was no gas, which
could be caused by no Hall pulses or a myriad of other things, I'm
sure.  Just went to 0, then back.  Did that repeatedly for about 30
minutes then never again.  This was in a dry desert environment, right
after sunset.

-jeff