When a car sputters, there is usually a problem with the exhaust system. When an engine sputters, there are a number of possible causes. If a loud bang accompanies the sputtering, especially when the car accelerates, this indicates a problem with the exhaust system. One needs to inspect the exhaust and muffler for holes or blockages to determine which part needs to be repaired.
One common cause of an engine sputtering is a malfunctioning battery. If the sputtering occurs when the motor is idling, this is the most likely cause of the sound. Another common cause of engine sputtering is bad spark plugs. Spark plugs also cause an engine to sputter when oil has come into contact with the spark plug well. One diagnoses this by testing the spark plugs and visually inspecting the well.
If the car is fuel injected, a blocked or malfunctioning fuel injector might be causing the problem. When this is the cause, the inspector hears a clicking sound addition to sputtering. It is also possible that a break in the fuel delivery lines is causing a loss of power to the engine, which causes engine sputtering.
Ultimately, the best way to figure out why a car or engine is sputtering is to isolate where the noise is coming from and find out when the noise occurs.