Quote:
Originally Posted by Volvomassa
Hi. My Volvo 960 II -97 2.5 Automatic vibrates when I accelerate from 0 to 40 km/h. It may calm down if I drive neatly but sometimes whole car vibrates. Also if I'm on lights and idling, I can feel the steering wheel vibrating mildly like the engine was running roughly. Any ideas? 
The drive shaft support bearing has been changed and this may be worse after that. Does badly assembled drive shaft support bearing feel in the driving wheel when driving?
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It's quite comon for the propshaft centre bearing (drive shaft support bearing) to not find its vibration free position when first fitted. What has worked for me and several others is to crawl underneath (do NOT jack the car up) and slacken the 4 retaining botls on the centre bearing by 1/2 a turn each.
Take the car for a short drive, accelerating gently to the speed it vibrated worse at or just over and return home.
Crawl under again (without jacking the car up) and tighten the 4 bolts evenly, a little at a time. Once completely tight, take the car for a test drive to confirm it's now vibration free. If not, repeat the process. Usually only takes one try though.
As for your other problem, it sounds as if the IACV is blocked or not working - the fuel ECU is meant to bring the idle speed up to cover extra electrical load such as lights, heater/A-C fans etc when idling.
Also when was your ATF last changed? Old/dirty ATF can cause a lumpy idle, almost as if there's a heavy misfire.
I'm guessing you've already checked the basics such as plugs, distributor cap/rotor arm or coil packs if it has the instead.