My 1982 240 k-jet has an intermittent bucking problem. Well, I guess you could call it bucking, I don't really know how else to describe it. The problem occurs during accelaration--usually in 2nd gear under some load. In its worst form the car shakes violently fore and aft. It's crazy--like a bucking bronco. I can pretty much sense when this bucking is about to happen, so I drive smoothly and slowly enough to avoid it, for the most part. Hints of the bucking can be felt at other speeds, but only when under load.

For several weeks I thought the problem was a completely deteriorated center driveshaft support donut (I thought the shaft was banging from side to side, cause the whole vehicle to buck back and forth), but I replaced the rubber and the problem persists. Could it be a fuel delivery problem or what?