Pontiac Repair: 94 bonneville running hot, electric cooling fans, coolant temp

Question
My 94 bonneville on the highway stays cool in between 100 and 200 degrees but on a main street (with traffic lights) she starts running hot even with a new thermostat, antifreeze, and no leaks coming from water pump. I've taken it to a couple of so called mechanics but they can't tell me what's wrong with it. Whenever they try to read the codes on it they say it has to many strange codes from different parts to figure out. I like my car and would like to see it running like these newer cars. What should I do?

Answer
Hi KD:

When you say it's running hot how hot is "Hot" are you just basing it off the temp gauge or does it actuallt boil over. does this truely have a 50/50 mix of antifreeze and water it not it can effect the cooling and the boiling point of the mixture. How about the pressure cap is that new? has anyone put a scan tool on this and verified the temp of the engine coolant temp sensor/the temp gauge? what codes does this set? that is a starting point. The answer you got is a BS answer. codes storing are a clue as to what is going on. Do the electric cooling fans turn on and run. Does the A/C still work on this is so turn the a/c on and after a minute or two the fans should come on at least at slow speed if not then ther could be an issue with the fans or the control of the fans.
good luck :-}