I've got a low idle code, P0506. I cleaned the MAF and pulled the hose off the PCM to see if that made a difference. Nothing.

Idle drops to about 400 and engine dies, especially when applying the brakes and turning (parking or slowing down quickly).

I'm not sure what to check next.

 

Idle Air Control valve. Might be able to clean it, but they are fairly cheap to replace if you've already taken the time to pull it out.

 

3 valves don't have iac valves. But it does sound like iac that's what I thought for a second too till I saw his signature line I've seen some throttle bodies cause some wired stuff and is kinda where I'm at if it is a 3v. If this is the truck in his signature it would be a 3v but he doesn't say. Op What are you using to pull that code and is that the only code your getting.

 

Yes, it's the truck in the sig. I have an el cheapo code reader from Wal-Mart. I thought IAC Valve at first too . So, I'm kind of at a loss. That's the only code and it comes up consistently (after clearing it).

 

Sorry, missed that part. Symptoms sounded spot on for a bad IAC so I didn't even bother to read the year.

When was the last time you changed the air filter and spark plugs?

 

I would start with checking the air filter like mentioned above replace if dirty then check for vaccum leaks and clean the throttle body. The 3valves also had problems with the cats clogging up in some years don't remember which years were affected off the top of my head but crawling under the truck and giving them a good tap with your hand and listening for rattling in them is a good indicator there is a blockage obviously do this when the truck is cold.

 

I've had the problem on my 05 250 V10 twice.
The first time an arrogant service manager insisted the only solution was a new throttle body for a lot of $$ even though I presented him with the correct information in the link below
I went home and fixed it myself in less than 30 minutes.

This may or may not be your issue, but mine was related to extended time with a dead battery (my truck stays parked a lot). In that situation, the PCM can lose its programming for idle control and needs to be reset.

Here is a good article on it:
05 F550 V10 extreme low idle on start up with no accelerator