Hi I have a 98' S70 GLT with 76K miles on it. I haven't experinced any signifigant issues yet with this car. But... I do have a situation where at idle one can hear and feel a bad harmonic comming from the engine. (like a shake or a vibration) between 900 and 1900 RPM, I brought the car in to the deealer stating the same issue here. The dealer says "well the car isn't showing any trouble codes so it appears to be fine" Doh! i guess the dealer mechanics rely too much on thier PC's and don't do too much falut isolating the old fasion way. I don't own a service manual so i don't know where to start with checking timeing and such. Soo should i bring it back down to the dealer and be stearn about my problem or does someone have an idea that will better fit my siutuation

Take it back to the dealer and have them look at the RIGHT motor mount. Your car has 3 that support the engine- front, rear, and right. It is located under the crankshaft pulley for the serpentine belt. When these mounts collapse, they tend to cause the symptom you describe.

Dave the Volvo Tech
'99 V70R AWD, '93 854 GLT, "82 242 DL, 4 more in family fleet
Master Volvo Tech since 1985- 5 time VISTA Finalist

Well, the dealer guys might be right in not wanting to jump into trying to cure what you deem is a problem if they don't think it's really a problem. There are NO adjustments such as timing, it's all electronically controlled.
What you might be refering to may not really be a problem as I've heard what I think you're describing with many FWD Volvos. It "could be" an engine mount going or something very minor that's causing the noise.