These days, cylinder deactivation, or variable displacement, is relatively common — the 2008 Honda Accord V6 has it, for instance. And it's a beautiful idea. When the engine is running at light loads, it's logical to shut down unneeded cylinders to save fuel, like turning off lights in unused rooms. But in 1981, when semiconductors and on-board computers were still in their infancy, variable displacement was a huge technical challenge. GM deserves credit for trying, but the V-8-6-4 was the Titanic of engine programs. The cars jerked, bucked, stalled, made rude noises and generally misbehaved until wild-eyed owners took the cars to have the system disconnected. For some it was the last time they ever saw the inside of a Cadillac dealership.