If a vehicle sputters even when giving it gas, it is possible that the fuel filter is clogged or the fuel pump is failing. Other causes could be the ignition coil, spark plugs or wiring.
The best course of action to take is to start by replacing the fuel filter, which is fairly inexpensive for most vehicles. Next, replace the spark plugs and wiring, which is also a fairly inexpensive fix. If this doesn't fix the problem, use a product that cleans the fuel system, which can be found at most auto parts stores. If the problem persists, a more expensive part such as the fuel pump may need to be replaced.