Engine hesitation while warming up
 

I have a '92 Volvo 240 wagon with 203k miles. Recently it has started hesitating and sometimes even stalling out at stop signs until very well warmed up. On my previous models of 240 (two '72s and one '76), if I remember correctly, there was a cold start valve that would cause a similar problem when needing replacing. However, I don't think this engine has a cold start valve but must have something similar. The Haynes manual I have, even though it states it is for 76-93 models, is pretty much worthless for these later years, in my experience. Any suggestions are greatly appreciated.
Second question would be whether anyone knows of a better manual for these later 240 models.
Thanks, Prairie