Karen -
I occasionally get the same thing in my '91.  Has been difficult to diagnose
but generally happens in damp, moderate weather after the engine has partially
warmed up . . . moisture perhaps?  Anyway, a couple of bigtime revs of the
engine while in neutral usually eliminates the problem.  One other time, I did
get a different, less fixable kind of hesitation, and it turned out that the
fuel injector ground wire had become disconnected.  You might check that too.

Good luck,
Sam
'91 Carat
Philly