2000 cadillac seville sls

The underheating is one thing, but I have never heard of low power until it warms. The lack of warming could be due to a thermostat that is stuck open, or improperly regulating temperature. Is there a check engine light on by chance?

The check engine light does come on.Well sometimes it comes on and other times not. It is a strange thing that the car wont pick up speed until the car finally heats up . That takes about 15 mins.you'll hear the engine going and the car just really isn't moving fast. I have to push it to get to 30-35mph. Once the thermostat line reaches the center it will run fine but it takes some time to get it there. It is a pain every time I have to drive it.

If the engine free revs, and the movement is poor, then I would suggest the transmission is slipping, you may want the fluid checked when cold. It would seem that 15 minutes is a long time for the engine to heat, these usually warm up rather rapidly. If you press your info up, and the on/off buttons together with the key on, all the segments will light up, and your info center will display ALL?. Press on/off again and it will display ALL CODES?. Press on/off again and record the codes. It will display them for each module in alphabetical order. The ones you are concerned with are PCM codes. There is a way to get straight to PCM, but it is easier to describe the ALL option. The info up/down will toggle functions, and the on/off button selects functions. Report which PCM codes you recorded, and we can see if they have any pertinence to your symptoms.

I am going to do try that. Thanks so much for the help. I will let you know how it goes.