Will not run correctly

I have a 1991 Park Ave and it quit running. It didn't have any spark, so I replaced the coil pack and it started right up. That night I took it out and it runs, but it like flooding out. Sometimes it runs good and sometimes not. I've talked to a couple of people and they seem to think I should replace the Crank Sensor. I've bought a new one and don't exactly know where it goes and what kind of a job it is. Can anyone help me with this problem?

I would check the installation of the coil pack before you move on to another problem. It is really easy to mix a wire with another in the install--either in the coil itself or the plugs to the coils.

I mixed them up once and the engine would run, but it would run very choppy and wanted to die if I let it idle too long.

A bad crank sensor stalls the car completely or Jerks violently suddenly from running normally at speed. Been there and usually throws Camshaft Codes.

Yours sounds simpler.. like bad plug, plug wire, coil pack, etc.
Coil pack may fail at higher speed than idle which makes it more difficult somewhat. If the RPM dropps to a specific rpm. .Like say 1000 to 800 . more likely its a wire or plug. .etc.
make sure your AC isnt on.

Try to note whether its a loping failure or a random miss.
Loping means its associated with a cylinder or coilpack, or injector, (or vaccuum leak at that cyl).
Random would mean somthing else. Camshaft sensor. Fuel pressure. bad gas. choke on. etc.

I know this isnt as clear as it should be.. But may help.