My best guess would be the left motor mount has separated. The symptom of it happening when you turn left would suggest the motor has gone floppy when its weight throws it to the right. Turning to the right pulls on the (still good) right mount. The mount and motor will look normal even idling. Just grab the top of the engine and shove hard right and left. If there is a bad mount it will lift and you can see the rubber torn and swollen from age. Best to change them both even if only one is parted. The pulsing could be that the gas linkage is affected when the motor flops. Motor mounts is a common replacement issue with old volvos especially if oil has leaked on them. No biggie, easy fix.