97 Saturn SL Problems

Well I got my 97 Saturn SL with 109,000 miles on it and it ran great. The only thing i noticed was the temperature gauge never went past the first tick mark even after driving it for a while. Then I started to notice that it would boil over(still showing no change on the temp gauge) when in heavy traffic or at a idle for a long time. Anyways I found out the fan wasn't turning on unless I turned on the AC. So I checked the fan relays, motor, all good. Then I replaced the tempature sensor and the thermostate, redid my fluids, and checked my hoses. Now the temp gauge goes close to the middle tick mark but dosn't go all the way to trip the fan switch. It dosn't over heat but the fan still dosn't turn on. And yes I can tell when the fan turns on. Also its started to run like crap. No power and a really rough vibration when Im at an Idle. I've tried cleaning my intake and throttle body but with no sucsses. I also know its not a blown head gasket becuase i got that test done. Any suggustions and dont give me simple things like spark plugs becuase I am knowlagable about cars and have gone over all the little stuff that any nimwit can do. Please some really suggustions

First pull your trouble codes and see what the computer does not like. If you are not overheating anymore the fan may not turn on.

hehe, "I've checked everything, I know what I'm doing, and there's nothing wrong"

Well, then I guess it should run right :D

There are 2 temp sensors, one is for the gauge, and one is for the computer. With a scanner, you could view what the computer *thinks* is the temp of the engine, and verify whether or not the sensor is working properly. Or you could try replacing it.

I don't know what "test" was done for the headgasket, but keep in mind that its not always obvious or easy to diagnose one conclusively.

And here's your simple option: Have you pressure tested the radiator cap?

the rough idle and lack of power sounds like a misfire. Spark, compression, fuel. Process of ilimination