Q: My car buckle and jerks real bad but when I put fuel treatment in it stops until the fuel gets low.

It sounds like you may not have fuel injectors that are firing properly or that may be a bit clogged. When the fuel injectors are not spraying an even, uniform pattern of fuel, this causes an imbalance in this air fuel mixture resulting in the motor often times starving for fuel or in some cases being flooded with too much fuel. In cases where there is too much fuel being provided (i.e. a leaking fuel injector), this may cause the engine to bog down and produce a fuel smell and occasionally, emit a bit of black smoke from the exhaust or cause problems with starting. In a situation where the fuel injectors may not be providing enough fuel, this may cause the engine to starve for fuel often times resulting in the car jerking or bucking while driving as a result of the intermittent fuel supply. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.