Misfiring is yet another culprit behind engine vibration. Modern ignition and fuel injection systems, which include better spark plugs and intelligent engine management computers, are far more reliable than the distributor-based systems of yesteryear.
That said, misfiring can (and does) still happen on newer vehicles. During a misfire, one or more spark plugs fail to fire and ignite a fuel pulse when they're programmed to. That failure to fire in one or more combustion chambers causes a hiccup in the rhythm of the pistons, and as a result, the crankshaft to which they're attached. The result: vibration, jerking, and even engine stalling. Now for the innovative part: if you can't tell the spasmodic vibrations of a sick engine from a merely old and pokey one, today's technology has you covered. It's almost certain that a misfiring or non-firing cylinder-spark plug combo will trigger a "check engine" light on any modern car. From there, you can use an easy-to-find and purchase diagnostic reader to determine what's wrong, or bring the vehicle to your local service shop to have a technician take a look.
At its heart, unwanted engine vibration is about a lack of harmony. As we already noted, internal combustion is a pretty violent process to begin with. Our next innovation is one pioneering man's attempt to bring some harmony into the equation.