Steve,

The problem sounds electrical to me. It actually sounds like the temp. sensor
II is not right. If the alternator was replaced it is possible that the wire
to the sensor was somehow knocked off, it sits very close to the water pump
pulley, or is somehow not making a good connection. This has happened to me
with the same results as you are experiencing.

The reason it runs fine for a couple of minutes is that the ecu by passes and
runs in open loop at start up for a couple minutes.

Do you know where the temp II sensor is?

Check the connection and follow the wire (mine had a break in the wire) as
far as you can.

Also do a basic check in the engine compartment as others have advised. Make
sure that everything in connected.

I live in Florida. Orlando. P-Mail me if I can be of any help.

Ron
Orlando, Florida