I get the impression you have a charging system problem. In addition to that, since you had to disconnect the battery to replace it, the Engine Computer lost its memory. It is going to have to relearn "minimum throttle" before it will know when it must be in control of idle speed. Until then, the engine should stay running if you hold the gas pedal down about 1/4".
To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals.
The engine should run for at least a half hour on the new battery. Once minimum throttle is relearned, or have a helper hold the gas pedal down a little, use an inexpensive digital voltmeter to measure battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, suspect worn brushes in the alternator, but we'll need an additional test to confirm that.
Friday, April 22nd, 2011 AT 1:23 AM