Code P1506- '99 Windstar 3.8L Idle problem

I had the metal tube between the intake manifolds leaking a couple weeks ago. Based on the forum and seeing 171/174 listed alot (so I had to check it out) I replaced the pipe and then while having the cowl off changed the plugs, wires, all the rad/heater hoses. Also changed the isolator bolts and upper intake manifold gaskets, cleaned the egr port per Lockemby site.
Every thing was fine except a high idle speed of about 1200 at idle. Today the check engine light comes on. Checked at Autozone showed P1506 Manufacturer Control Vehicle Speed Idle Speed Control Auxilliary(What the tech wrote down). I noticed today when I shift form Park to Drive it will rev up to just over 2000 rpm and then slowly creep back down to about 800.

Can anyone help me with this? I had cleaned the throttlebody when I had the intake off. Should I try and clean the IAC again or is it possible something else?

Also in the back (passenger side) of the upper intake where vacuume lines attached is a round cover. Did I do something by turning this or is it just a cover. I did not understand what it was for or if I messed it up.

Hi

I show that it means "idle air controller overspeed error". You could try cleaning it again or go for a replacement. As to the cap you turned, I think it was probably the top of the EGR solenoid. It is designed to turn freely, so I do not think you hurt anything.

Okay I was finally able to work on it this afternoon and took off the IAC and cleaned it. The check engine light is still on and the idle is still around 1200 in Park.
Does anyone know if I need to have a certain number of starts before the light resets itself?
If not should I go ahead and change the IAC or is there an off the vehicle test that can be done to the IAC?

Also I forgot to mention that I had replaced the IAC back in September.
So is there something else going on causing the problem or is it still that I should replace the IAC again?
Thanks for all the help.

Okay the light has gone off today so maybe it takes a few starts to clear the code.
Can someone tell me what the correct idle speed should be in Park so that I can adjust it? Mine is running around 11-1200 rpm which seems to fast.

Hi
My '96 3.8 idles around 6-800. However, I don't know how you would adjust it. It is not designed to be manually adjusted as were older vehicles. Have you made sure that your throttle/cruise control linkages are free and not binding (just a stab in the dark). Also, I had an '87 Ford with throttle body injection that idled high. While in for a recall the Ford mech noticed it and changed the pcv valve, which fixed it.

I don't have anything definitive, but I believe the idle is set "electronically" and there is little you can do.

1. YES it does take a few start & run cycles to clear the CEL.
The reason for this is to hold the code long enough for you to be able to get a diagnostic......in case of intermittent problems that seem to go away once you get it to the shop.

2. The idle speed is set by the PCM (computer).
Now, the post about the PCV valve......is along the lines of too much air still getting into the engine.
It could be caused by the IAC, it could be from someplace else.

As mentioned, it is possible that the throttle is somehow partially stuck open.

I had a similar problem after cleaning the throttle body and IAC when I did the lower intake gaskets on my 96 3.8L. I had to clean the IAC repeatedly, maybe 5 or 6 times, to get the crud off of the little disk inside. In fact, I had to use a pick to get of the remaining spot of crud that was causing my problem. Holding it into bright light may help. I had a very sunny day when I spotted the remaining crud. I had never seen it on the several previous attempts.

Idle speed is aroun 750 rpm normally.

I finally made it through a week with the CEL off. This after repeated cleaning of the IAC. Hope that is it for this problem.
Thanks for the help.