I have a 2004 ford focus zx3 2.3l. I am having a problem that is semi hard to explain. When I bought the car it had over 215000 miles on it. It now has over 222,000. When I got it there was a check engine light, p0420 catalytic converter. I got that replaced. The problems are 1. It accelerates up to at least 25 MPH without me putting my foot on the gas pedal. 2. I have high rpms when idling and it seems to jerk the longer I'm idle. When the jerking happens the rpms drop below 1,000 and return to just above 1,000 and sometimes this jerking happens multiple times in a row. When I release the brake it continues until my car gets to about 15-20 MPH. does anyone know what makes my vehicle do that?