p0505 code

This code refers to a malfunction in the Idle Control System. I would look at the idle control valve, they are problematic on Fords. Sometimes they can be cleaned, but sometimes they need replacement. There are some other considerations as well, this is from the repair manual: Trouble Code Conditions: Engine started, engine running at hot idle speed, and the PCM detected the Actual Idle Speed was too low or too high when compared to the Target Idle Speed during the KOER self-test. Specification: The IAC valve resistance is 6-13 ohms at 68ºF. Possible Causes: * Air inlet dirty, restricted or the air cleaner is severely restricted * IAC solenoid control circuit is open, shorted to ground or to B+ * IAC solenoid power circuit (VPWR) is open from the relay * IAC valve is damaged or has failed * PCM has failed * TSB 03-3-5 contains repair information for this trouble code