i have 2005 sentra 1.8. about a month a go, i had my car serviced for some valve in the gas tank. the tank was acting like it was full and wouldnt let me fill it. got that fixed. since then, when i start the car, it would shake for the first minute or two, but after pulling off it would be fine. just yesterday i was on my way home from work, and the car starts shaking violently as if i was being pushed/pulled from behind, won't let me get higher than 2500 rpms, and the temp gauge started to rise significantly and almost overheated. WHAT IS WRONG NOW?!!!!!