90 100q stalls out

[Dave C]

 You wrote:
"My 1990 100q, manual, non turbo stalled out at the mall ... "

Sounds like an intake air leak.  Check the rubber hose attached to the ISV,
the hose that runs toward the back of the engine, hidden under the intake
manifold.  You probably need to remove the hose to give it a proper "look
see".  This hose tends to split along a seam.  The split tends to open up
more when the rubber gets hot from engine heat, like sitting in the parking
lot with hot engine.
HTH
- -
Dave C.