My F250, 5.4 will not idle right. Sometimes it idles around 1500, sometimes it will not idle at all. If I use the clutch to slow down rpm will drop to 500 and sometimes the engine dies. Will the throttle position sensor cause this problem and if so where is it located?

 

Check the IAC (idle air contol motor) behind the throttle body.. Try and crack open the throttle 'very' slightly,does the engine/idle smooth? Check the PCV and hose as well,and attachment to the back of the intake.. Any check engine light?