IAC Replaced - P1506 Error Code (High Idle)

[apex2012]

I've looked through the forum before and found some possible solutions, which I have tried to no avail. I have a Ford Explorer Sport 2001 (4.0 SOHC), which I recently replaced the IAC. About a week after, I started receiving the "P1506 error code: Idle Air Contol Overspeed Error" and my idle is around 1400rpm (less when in gear). Here is what I have done to troubleshoot the problem:

1.) Unplugged the IAC, and let the vehicle idle
Result: Idle stayed between 500rpm - 700rpm while IAC was unplugged, but was very rough. When the IAC is plugged in, no rough idle at all, but idle stays high around 1400rpm.

2.) Cleaned the MFC (with MFC cleaner)
Result: No change

3.) Unplugged the battery for 30 minutes, let idle for 15 minutes after reconnecting
Result: No change in idle. Computer reset, but error code reappeared within one day

My next step is to replace the PCV valve (having difficulty finding it on this motor).

I figure it would be fair to mention something I feel may have contributed to this problem. A week or two before my IAC completely died (tried cleaning, no go), I washed the inside of the engine compartment. I'm not sure if this contributed to the death of the IAC, but I figure it may very well contribute to the rough idling when the IAC is unplugged. Also, I checked and I am not getting any misfires.

Any help would be much appreciated.

 

[2000StreetRod]

PCV Valve location

It's not likely to be your PCV valve. This shows where the PCV valve is on my 2000 Sport. SOHC PCV Valve Mod thru 2000 I don't know if it's the same place for yours.

When you cleaned your IAC valve did you get the gasket back on correctly and sealed? Since it doesn't idle fast with the IAC valve disconnected, it sounds to me like you have a bad IAC valve. Do you still have the old one to put back on and try? If not, can you take the new one back claiming it to be defective?

Have you checked your TPS voltage? It should be about 1.0 volts at idle.

 

[apex2012]

In regard to the gasket, initially I had left the old one on in a bit of haste. I thought that may have been the problem, so I installed the new gasket and made sure everything was sealed - same result. Thanks for the link, I was finally able to find the PCV in the same spot. I'll be installing the PCV as soon as the rain stops tomorrow, and testing the TPS voltage. Thanks again.

 

[apex2012]

So, things have turned a bit strange at this point. Before moving forward with checking the TPS and replacing the PCV valve, I looked over all the hoses/intakes/housings to make sure things where secured. It turns out, I did not correctly secure the MFC housing/intake tube on both ends.

Now comes the strange part. I fastened them correctly, made sure there where no leaks anywhere and that all vacuum hoses where fastened securely, and now when I unplug my IAC the Explorer dies. It still stays at 1400rpm when plugged in, but now when I unplug it, the vehicle dies instead of staying around 500rpm - 700rpm.

 

[apex2012]

Tps

Have you checked your TPS voltage? It should be about 1.0 volts at idle.

After everything I'm reading, I'm really starting to think along your lines - that the TPS is probably the culprit. I'll be testing it out next week.