my old (133k) 960 wagon's "check engine" light just came on. had recently started idling rough, and since it is well after a fill-up, i suppose its an emission item. while i dont have ready access to a volvo code scanner, we do have OBD II capability where i work (a Lincoln-Merc dealer). I hate to spend ANY $$ checking it out but i could get it checked for less $ there than my "friendly" independent vovo guy.
any quickie ideas on what usually triggers that first? on all my FoMoCo stuff, i go straight to the idle air control valve and clean it out, and if that doesnt work then i clean out the EGR. sad to say, on vovos i am pretty lost.
(at least on my 94 850 i can use the self diagnostics and my trusty haynes manual! had the ol' check engine light on for years and even the dealer and my indy guy hasnt been able to make it go away for good! lol best fix for that was a piece of electrical tape over the light!!!)

 

When ever I had a simular problem it was missing. Like cylinder #3 or something like that. I assume this has already been addressed but let the code reader tell you what the problem is.

Then please post back so others can benifit.