Chevy GM LS engine Active Fuel Management DOD AFM Delete Kit With Lifters. The hydraulic lifter in a car’s engine uses oil pressure to adjust a plunger and take up all the clearance in the valve train. This helps to ensure less engine noise and longer reliability, due to less wear and tear. Hydraulic lifters can begin to fail through the normal use of a vehicle. After several years of running the engine of your vehicle, the hydraulic lifters within the valves can become laden with sludge, and other contaminants in the valve, that they start to wear out. New hydraulic lifters can make a tremendous difference in the way that a vehicle runs as well as how the engine sounds. Be sure to have your engine lifters replaced with aftermarket replacement engine lifters as soon as it starts to give you trouble.