Possibly the fuel pump is overheating and shutting down, or the fuel pressure regulator is the problem.
when i changed the bm everything worked fine.$60 for the part.
I don't see why not. You'll probobly have to switch all the accessories for it too but The deville hasn't really changed very much since 1994 in fact in 94 it came with the option of the 4.9 and the 4.6 Northtar that comes standard in the 01.
The power steering pump on a 1997 Cadillac Deville is changed by disconnecting the pressure hoses, draining the fluid, and unbolting the pump. It is then pulled from the vehicle and a new pump mounted in place.
It is probably your egr valve that needs replaced!
If, with power applied, the pump provides sufficient fuel pressure at sufficient volume, then it does not need to be replaced. Otherwise, it does.
cracked head, or leaking head gasket, or cracked block
did the parking brake get set, or the shoes adjusted too tight?
change the oil pressure senser in the front of the motoer on the bottom just did it on mine
Heater core (radiator) needs to be cleaned or changed
There are two engines types for the 1996 Cadillac Deville. The 4.9 L and the 4.6 L Northstar. The 4.9 L engine's starter is accessible from under the car like most cars. The 4.6 L Northstar however, hides the starter underneath the intake manifold. I just recently changed mine. It took about 8 hours for the entire job. I think it would have been 6 if I was mechanically inclined.
If it is leaking coolant. And you changed the thermostat. I would then move to this section. Flush the radiator and the heater core. This can be done at a certified shop with a reliable mechanic.
Maybe check both electical fans between radiator and engine.