Have to push gas pedal to the floor to get car started

I have a 97 SC-2 Saturn with 134,000 miles on it. Its a manual transmission and I have had no problems with my car since I have owned it. I bought it when it had 80,000 miles on it. I have only had to replace the water pump. I have two things that are going on with my car and both have been getting considerably worse as time goes on. First the temp gage will move as it normally would and the car blows HOT heat and after awhile the temp gage moves down to C and wont move and the car still blows heat but not as hot and then the Temp Gage light blinks for a little while and then shuts off. Next when my car is warm if I go to start it it will want to start but wont turn over. I have to hold the gas pedal to the floor to get it to start then black smoke comes out of the car and it is fine. If I hold the gas pedal down to the floor while its running it wont go pase 3500 RPM's and when I am in first gear and want to go I sometimes have to hold the gas pedal down to get it to go. Could it be a sensor?