[mpj76]

Not sure how a ground strap would cause vibrations like you describe. How did you check the balancer? It is the solid piece BEHIND the pulley. Just wondering. Checking the little bolts for tightness wouldn't be good enough. Those dampers are actually two pieces with a rubber piece sandwiched between. That rubber can break down over time with heat and chemical exposure. Especially if you have a power steering leak. Also check tightness of fan to pulley bolts. Any loosness there will rapidly destroy your water pump as well. Sometimes an aging belt run accessory such as alternator or smog pump will start annoying vibrations. A quick test is to remove the belt and see if the vibration is still there. Do this for a short time only so you don't overheat the engine as the water pump won't be spinning. At least that will help you pinpoint it. Bearings going out in the distributor will also cause vibration.