Here's the deal, I just finished putting a used engine in my 2003 focus with a Zetec after hydrolocking my old one. The place i got it from claimed it had 62k on it, the issue I'm having is when I start it up it revs to around 4 to 5k rpm and stays there. My fellow mechanic friend and I have checked for vacuum leaks, changed the IAC, cleaned the throttle body, changed the engine temp sensor, and I just changed the intake manifold today hoping that was it but nothing has changed. I need my car as it is my daily driver and would really appreciate any advise as to what could be the problem. Thank you all in advance.