Cadillac Repair: 97 eldo etc, vacuum leaks, quality scanner

Question
my eldo runs great at night when the weather is cool.during the day i get a rough idle and the car runs hot.the code that keeps reappearing is pcm300.i have changed plugs,wires and also the ox.senser by the firewall.my air conditioning is blowing warm and i had the whole system replaced last summer@ about $1300.00.I suspect some sort of sensor is not functioning but i am at a loss.the shop that replaced my air conditioning system is out of business so i cant go there(so much for warranty )i have a new radiator,cap,thermostat,and all hoses have been replaced.my tags are coming up and i need to smog but im reluctant to take it to be smoged until i fix this problem ive been chasing for much to long.thankyou for any help you can provide.

Answer
What you have is a misfire that can be caused by:

Igntion control module.
ignition coil.
Vacuum leaks.

What you need is a quality scanner that can take SNAP SHOTS of the cylinders that are miss-firing.

Normal operating temp of the cooling system is approx 220 degrees.

I can Email you all the information that I have on this problem. E-mail me at: onlineautohelp@msn.com.


As to the A/C, Is there freon in the system ?. Does the computer display and other codes besides P0300 ?. If there was a faulty A/C sensor you would get a code. What EXACTLY is your A/C NOT doing correctly ?.