1997 Grand AM overheating problems

I need help my car is driving me crazy! My car has a funny overheating problem. When the temp is 70 degrees out side no problem it stays cool on the inerstate or in town but when it gets around 90 degrees then it has issues. I commute 1hr to work one way each day, when gets to be 90 degrees or warmer it stays cool on the inerstate but as soon as I get into town it starts to warm up very fast. The fan is function correctly and in the last six months I have had the head and intake gaskets, and thermostat replaced. I don't know if it is related but the check engine light has been on the whole time this is going on. I had a shop hook a computer up to it and they said it could be a vaccum leak, or oil in the engine where it's not suposed to be. They weren't much help, I think the code was AP204? I don't know if this light is at any rate related to the over heating problem or not. I need some help from all you grand gu-rus out there. Any ideas?

Probably your water pump is failing. Our vehicle temperature goes up while idling at a stop light and goes beyond 200 degrees and when at the highway, the temperature just barely to 190. I've noticed my coolant is getting low for about 2 weeks and I have to add some coolant.
Finally, I let the vehicle IDLE for about 30 minutes or more and then I finally see the coolant drip from the water pump. The water pump was pain to remove because it way behind the engine and I have to remove the exhaust manifold just to get to the water pump.
After the water pump was replaced now the temperature is around 160 most of the time even when idling for period of time.

When was the last time you have flushed your coolant? Green coolant is suppose to be flushed every two years because its high boiling point goes down and its anti-corrosion wears away.

You might want to help the engine cool down faster by adding a manual switch for your radiator fan so you can manually turn on the radiator fan when idling or driving in the city at most stop light.

I have a 97 grand am 3.1 v6. When I first got it I had the exact same problem. I replaced the thermostat with the same problem. So I called a radiator shop and asked if it could be the radiator, they said yes so I replaced it and havent had a problem since. Hope this helps

Very interesting , it is a common fact that engines stay cooler on the highway and get hot in town , this is a trademark of gm and is common , the engine gets hot and sluggish when you drive in town (stop and go traffic) , i had an argument about how the shop should go about fixing it. After arguing witha gm service advisor and taking him for a ride to prove it to him , he decided to take me for a ride in a low mileage one that was a couple years newer same engine ect... newer and did it more often than mine espeacially in town. He showed me to use the defrost on high speed vents and full blast heat , cools the motor faster(giving the hot air a place to go) i use a lower temp thermostat and it does it alot less. But since i use a lower temp thermostat im losing the cooling fans life expectancy. It stays cooler tho.