How do I trace a IAC valve harness short or open wire

Question

I have a code p1504 on my ford f150 xlt replaced my IAC valve but the Idle still goes up and down eventually it shuts off. I checked voltage and its ok but its still the same. One I noticed is when I put the intake manifold back after repairing my heater hose on the left side rear of the engine I could see the manifold gasket and one the holes was visible that the intake does not cover not sure if its supposed to be like that. Can someone help please.

Answer 1

P1504 IAC (idle air control valve) What you describe sounds more like a vacuum leak than the IAC, You can code the IAC P1504  if the IAC was disconnected when it was running, As for the hole you describe if it is taking in vacuum that can be it. Wish you given the year.