Saab: black smoke coming out exhaust, black smoke engine startup

Question
When I start my saab black smoke comes out of the exhaust.  It sometimes only lasts a few seconds.  Yesterday it lasted 10 minutes.  Any suggestions? Need a new head gasket maybe??

Answer
Courtney:
 Black smoke at the exhaust is typically the sign of an "over-rich" mixture. It is often caused by an incorrect sensor input to the engine management computer, typically one related to temperature.A poorly functioning fuel injector or o2 sensor are other possible culprits. You did NOT mention a "check engine" indication. Without such indication, the problem is more likely mechanical.
  Since you did not mention the year, I cannot be more specific inasmuch as the fuel injection systems varied over the years.
  Hope this helps,

              Jerry
New head gasket--very unlikely.