I just got the maro out of the body shop the other day to get the window motors replaced, it was beautiful until I got about 20 miles from home and stopped for gas and overheating issues, noticed the cooling fan wasn't turning on and the gauge read 220+ so I sat at the station for a bit to let it cool down (full of coolant) and drove about 65-70 about the whole way home and it stayed around 230 240 on the gauge until I turned down my dirt road to my house and within about a half mile or less with the hood popped it ran to 260 and shut off in my driveway, since then it's given me no trouble starting but it idles like it has a carb on it flooding out. I haven't driven it since this incident but have checked for codes and it brings back nothing but code 12.

I knew I should have went SBC while I had the chance

 

I take it the car ran without issue until the time?

I would say that they messed up the wiring to the fan... hopefully on accident.

I am not sure about the engine issues. Only thing I could say is I would tear the engine down to check what might be up. But then again I like tearing down engines...

 

it either a bad fan relay or a bad fan switch,also might wanna check the water pump and go ahead replace the thermostat and u should be set for the overheating part.

but the rough idling part is a other issue, u might have a blown head gasket..

 

but if it was a bad relay/or wiring, wouldn't the fan not run while I'm scanning for codes. I'm thinking ECM time! The buick was doing something similar to this about a half a year ago, replaced the ecm and no problems since.