Try adding dry gas into the tank at every fill up, its possable that water is some how getting into your gas tank. You may also consider changing the gas you use and the gas station you fill up at.
One of the main causes for a 1998 Buick LeSabre to die while driving is a problem with the computer. The computer might tell the fuel pump to shut off and stop sending fuel to the motor.
The computer does it for you through the IAC valve Idle air control its under throttle body intake hose.
throttle positioning sensor
On top of the engine, drivers side.
On my 1994 Lesabre it is under the dash about center at edge of carpeting
directly on top of the throttle body intake
check for vacuum leak.
throttle position sensor believe it or not!
The Idle Air control valve is located on the side of the throttle plate.
the tps is bad-throttle positioning sensor
The Coolant Temperature Sensor on a 1993 & 1994 Buick LeSabre is located on driver's side of the car under the throttle body, It is screwed into the lower intake manifold. You cannot see it without first removing the throttle body since it is hidden under it. An electronic plug is clipped to the the end of the CTS.
... There is no carburetor in a '01 Buick... the last Buick to use a carburetor was in 1990. If you are talking about the throttle body, however, there is a butterfly valve inside, but the only way to get to it is to remove the throttle body.