All right guys, haven't posted in a long time, but I still lurk about. I finally have run across something that I can't figure out. For the past few months I have been fighting with an issue with intermittant high and hanging idle, as well as P0506 popping up. I have verified multiple times that there are no vacuum leaks. The IAC valve is new, as well as the MAF, timing belt (verified engine timing) and alternator (for the fourth time, keep swamping it when I wheel). I have been Google-ing my face off, but have been unable to find anyone else that has had this issue. Any ideas?

check your IAC valve. Also, for what it's worth, try cleaning your MAF...

As I said, the IAC and MAF are new. I've had this issue since before the replacement parts.

Is the TPS functioning properly? And is it in sync with the position of the butterfly in the tb? (0% when TB closed, 100% when TB fully open)

Only thing that comes to mind, haven't seen that code in my life.

Yeah the TPS was my next thought. I ordered one last night, and will install it today. I'll let you know if it works. If it doesn't, I'm going to go get another MAF (have lifetime warranty since I have a tendency to go through deep puddles, despite having the snorkel. <img src="/forums/images/graemlins/notooth.gif" alt="" />)

Well, TPS didn't fix it. I'm gonna try an get the MAF warrantied today, and hope that fixes it. Trying to get it ready for a wheeling trip this weekend.

Ok, just to update... I did not replace the MAF as apparently the "limited lifetime" warranty was limited to one year. <img src="/forums/images/graemlins/angry.gif" alt="" />

So, I was thinking maybe the throttle body was sticking open. Removed the throttle body, found slight carbon buildup, but not enough to cause that issue. I went ahead and cleaned it while I was there.

Since I had the throttle body off, I checked the PCV valve, which turned out to be stuck open partially. I went ahead and replaced that as well, just to be sure.

I then reset the computer (as shown in the KGIS website, pull the fuse for the pcm for at least 2 minutes). After resetting the computer, the vehicle was idling around 900 for the first time in probably 4 or 5 years. <img src="/forums/images/graemlins/kewl.gif" alt="" />

That is, until I drove it. Made it to the end of the block, and the Kia is hanging the idle at 3000 and up rpms. <img src="/forums/images/graemlins/angry.gif" alt="" /> Pull it back in the garage, check it over for vacuum leaks, make sure no connections are loose, ect.
Thats when I find that the TPS connector signal pin has a slight burn mark on it. I head to the junkyard and pick up another one (off a sorento, but same connector) and wire it up. Hooray, no more 3000 rpms, but still idling at about 1200.

I did a bunch more check, but I eventually started pinching off hoses, and found that the tank vent line from the carbon canister when pinched off allows the idle to drop. I've only driven it a couple of times so far, and although when warm it seems to idle a little high (1000 to 1100), it hasn't kicked the SES so far, and it still isn't idling crazy high. I'll post up at a later date if something new comes up, or if I get a different code with SES from having the tank vent line blocked off. <img src="/forums/images/graemlins/kewl.gif" alt="" />