Deceleration/ragged idle problem

["Tony" <roner@freeway.net>]

Car is a '90 200tq, 5 spd manual.  When decelerating at slower speeds (such as driving around town and coming to a stop) my RPMs drop below 600 and it runs ragged for a second or two until it goes back up to normal idle speed.  Additionally, idle is a little rough and will drop down below 600 (just for a split second) from time to time.  None of this happens when car is cold, only when it is at least partially warmed up.

 

Any ideas?  Vacuum leak?  Idle stabilizer valve?  Something else?

 

TIA,

 

Tony Fordham

Grand Haven, MI

'90 200QT