My car is acting really weird. When it is first started up it will act fine. then when i get going and the car warms up the rpms will start acting weird they will go down and up without me pressing on the gas also it is shifting weird at not the right speed and then the car when you restart it the rpms will start acting weird and yesterdday it wasnt even drivable it kept shutting off before i could gett it into gear and i had to keep on the gas for it to stay on