1990 Chevy Lumina Euro 3.1 running hot and rough idling, loss of power at times

I have a 90 Chevy Lumina Euro and my radiator fan won't click on until the temp. gage is almost in the red. Then it will click on. There are two relays for it, a primary and a secondary, we changed one but it still does it. We even switched them around and it still is running hot. Thermastat was also changed, any ideas for me? Also, sometimes when I am driving it will loose power, you press on the gas and it shakes a little then will pick up. Any ideas on that too? Thanks