Like other automakers, Toyota has left traditional carburetors for a more controllable form of aspiration: fuel injection. The primary benefit of fuel injection is that it can be electronically controlled, making it easy and quick to adjust engine performance on the fly for everything from humidity, temperature, load and altitude. Fuel injection systems are not without problems, however. Just like carburetors, with use they will eventually stop functioning normally -- usually from a blockage of the fuel flowing through one or more of the injectors.
If your Toyota has one or more plugged fuel injectors it will not produce combustion in one or more cylinders. It's possible for a plugged injector to completely stop a cylinder from functioning. It's much more common for the plug to cause intermittent ignition in the problem cylinders. The car will sputter. Acceleration will be jerky. The engine might die at idle or low rpm. There may be an acceleration lag: a slight sputter or delay, before the engine begins to rev. If there is a very slight obstruction, the engine may not sputter, but just feel unresponsive and less powerful.
Fuel injectors create a very fine mist of fuel. In spite of having fuel filters, small debris can become lodged somewhere in the injector, restricting or completely blocking fuel flow. The source of the debris can come from the fuel itself. Fine particles might find their way into your gas station's fuel reservoir. Fuel tankers can pick up debris. And, just like your gas tank, small particles can slough off the fuel reservoirs to become stuck in the injectors. Other causes are gum or lacquer caused from fuel additives. Fuels themselves are solvents; when dried, they don't tend to leave lacquer-like residue or gummy residue. The additives, however, do remain when the fuels dry. These left-behind additives can plug fuel injectors.
It's important to understand that plugged injectors are not the only cause of the dead cylinders, sputtering or cutting out. In fact the symptoms of a plugged injector are almost identical to a few other fuel problems and a number of electrical problems. Essentially, you're engine is not combusting fuel when it should be. The symptoms feel a lot like you're running out of gas. So, you want to make sure there is gas in your tank. The symptoms can also be caused by a clogged fuel filter or fuel line. And it can be extremely difficult to tell the difference between electrical problems and fuel problems. Anything from moisture in your distributor to bad spark plug wires can cause very similar symptoms. One hint that can help you figure out whether your problem is fuel or electrical is whether it disappears with higher rpm. As your engine accelerates, it creates more amps, which can jump across poor connections. Fuel is the opposite. Debris might settle when the engine slows and tend to clog worse as fuel moves more rapidly. Otherwise, systematic tests will be required to isolate the problem. Or, you can just clean or replace your fuel injectors.
