E250 cargo van-- bought from auction important question?

when i drove home from buying the van. the engine kept going and accellerating a bit when i stopped at the stop sign. what could this be... i think it may have sit for a long time with no driver just before i got it. ??? thanks for your adviceE250 cargo van-- bought from auction important question?
Bad throttle position sensor maybe. Not an expensive part either. Another thing to check is the accelerator cable to make sure that isn't binding, this could have happened from sitting.E250 cargo van-- bought from auction important question?
Take it in and have them check your O2 sensor. What the van is doing is called surging.