Loses power after about 45 min./ O.K after restart

I've not been able to drive this car since I've recently purchased it. Now I'm getting around to driving it and I've found once it reaches normal operating temp the check engine light comes on.

Next, after I drive around about 45 minutes it will lose all power/not pull itself. I shut off the ingintion and restart then its fine again.
Whats happening ?

Check for codes, because of the CEL being on.

Update:
I changed my thermostat and found alot of rust in the housing. After I changed that along with a new housing , I no longer have any of these issues. No check engine light or lose of power. Before I changed it the temp gauge never got about 3/4 hot. But now my temp gauge is not working at all. I think the sensor rusted while I had the thermostat housing off for a few days while waiting for my new housing to arrive from NAPA. Also, I found out my ECT sensor on lower intake was bad. I'm sure that had something to do with the lose of power.

The temp gauge sensor is in the block on the rear of the engine on the drivers side of the car. It wouldn't rust out, it may be bad however. As for power the ECT will effect the fuel delivery based on engine temp and that possibly could have ill effects.