Volvo Repair: Check Engine Light On; Car running rough, 1997 volvo 960, volvo dealer

Question
I have a 1997 VOLVO 960 Sedan, 6 cylinder, 258,000 miles.  I was driving the car when the check engine light came on.  The car immediately began to run rough, with a reduction in power (although I could still do 60).  Acceleration was a little slow, but doable.  Idle was rough, but it continues to run.  I do not have a diagnostic computer, so I do not have a code.  What could this be?  Do I need to go to a mechanic or can I try a few simple parts?  

Answer
Hey Karl,
          The many electronic systems that are now used are very expensive and require proper diagnosis...or you'll pay and pay for guess work.Even I..(mrsmartass)
go to the Volvo dealer for diagnosis'in complex problems...
          You can check plugs/wires/connections but pay them to tell you what's wrong....then you can fix it yourself...and save some money.

                           Good luck,
                                   Bilbo