Rumbling, stumbling, bumbling....idle

[david.becker@lw.com]

     Please help!  My '87 4kS has developed a (new) problem, and being 
     mechanically ignorant, I could use some advice from the List's 
     collected wisdom before I drag it in to the shop.  Right after 
     start-up, the idle drops very low, and the engine starts to stumble, 
     making the whole car shudder like someone's running a jackhammer under 
     the hood.  This corrects itself after a couple seconds, and the car 
     then runs fine, but it often repeats briefly once I put the car in 
     gear.  It generally doesn't happen if the car is warmed up, but it 
     sure is annoying, and makes me wonder if there's a serious problem.  
     Could this be...
     
        1.  compression problem?  :-(
        2.  idle stabilizer valve?
        3.  engine timing?
     
     Any diagnoses/suggestions gratefully considered.  Oh yeah, saw a red 
     200T, Massachusetts tags, on Connecticut Avenue in D.C. around noon on 
     Saturday.  Very nice.  Any takers?  
     
     TIA,
     Dave