Can the radiator fan start time be modified?

I bought last week this 89 grand prix with only 35,000 the previous and only owner didn't drove it a lot because of overheating problems. When I turn on the car the coolant light comes on until I drive like five minutes then off the same with the engine I could just be driving and the temp goes up from 170 - 210 to 250 - 260 in 30 seconds to 1 minute then the fan turns on and the temp lowers to 170 -180 couple of minutes or 1 hour later the same temp goes up, no coolant lost, No steam anywhere, New thermostat from 195 to 180, new radiator cap, New radiator sensor,New sensor the one tha is near the tesmostat And I bleed the system but no air is comming out just coolant but if I open the radiator the water is like boiling. so what do you thing is haappening and it could help if the fan turns at 220 or less instead of turning on at 250. Someone told me to remove the thermostat But I don't know what to do.

oh!! the engine is 2.8 FI

maybe a fan switch is bad? have you reset the computer since you got it?

Hi, No I have not, How do I reset the computer?

Disconnect the battery for about 10 minutes. This will reset the computer to default.