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Re-read post #11. The Idle Air Control (IAC) did not fix the codes, just the noise and the poster claims an improvement in acceleration. If there was an improvement in acceleration, it was from something other than the IAC. The IAC only comes in to play when the throttle is completely closed. It literally meters the amount of air that can bypass the throttle plate. Even slightly opening the throttle will allow more air to flow, with less obstruction, than the IAC and passage.

The codes are more likely due to a vacuum leak, probably intake gaskets, vacuum lines, or the PCV tube. It could also be due to the Differential Pressure Feedback-EGR (DPFE) sensor, but I'd start by checking for a vacuum leak.

-Rod

 

Same problem, the notorious P0171 P0174. Now, I am assuming that you already checked your vacuum lines with your mouth or a vacuum brake bleeder; making sure that your lines do not have holes in them and that they can widthstand suction. If you havn't done this; do this now! While you're at it, check hoses and other hoses connected to the intake that may just have a crack or hole aka. PVC hose, OIL cap, oil cap hose and that one going underneath your battery that even the dealer can't decide what it is or isn't. If you find a hole in the line or a crack, repair it, erase the codes drive 40 miles. If the light comes on again, continue checking the hoses and move on. I want you to know how you can distinguish the problem. I myself have been quite frustrated with these codes. Infact it has taken me one year to actually buckle down and find the issue. Like most of us with these codes, I replaced parts on this like it were a lego car. While reading more on these codes. (on a KIA website) I found myself fidling with my laptop in one hand and my OBDII in the other and I found a solution. Buy, find, or rent an OBDII scanner from your local auto parts store. Ensure it has Live Data feed software in the OBDII. Plug the OBDII in while vehicle is running; go the the Live Data feed menu screen and press enter. Next, see if you can find your short term fuel trim reading it should be as close to 0.00 as possible. (Mine was flexing from -3.61 to 7.62 that's when you know you have an issue) Once you see your trim reading scroll down to it and press enter. You will see a graph pop up like something you did in math class a thousand years ago; you will notice the graph is moving up and down, thats good, that means your vehicle is running. Now, pop your hood, get a can of Carb & Choke cleaner and spray it in and around the engine bay. Making sure you get in the tight areas around the intake manifold. If you notice a large change in the short term fuel trim graph reading (mine plumited and my vehicle almost died); around a certian area where you sprayed, you've just found your problem area. Ok. So, you found your engines bad spot. Depending on where your graph changed dramatically, I'm just going to assume it is the intake plenum gasket. Funny, what manufactures are doing these days. They're bolting plastic intakes to metal manifolds. Dumb right? Plastic heats up and expands at different tempuratures than metal, the dumb dumbs. Thus resulting in a defect later down the line; in hopes that you will bring your vehicle to the dealer. So, they can rape your wallet. I got the plastic intake off, I found just underneath that, there is a fuel rail and I just took it off aswell. When I went down to my local autopart store I got, the plenum gaskets, 8 fuel injector O-rings, some COPPER silicone HIGH HEAT, and a reverse Torqs socket to fit the head of the fuel rail bolts. Putting her back together, the fuel rail bolts need to be torqued to 11LBS and the intake nutts need to be torqued to 12 LBS. Hopeing you got the hint on the COPPER HIGH HEAT silicone. After she's back together, I drove to no-where and back and no codes, she is running like a champ. I recommend doing this first before you change the Mass Air Flow sensor (MAF), Idol Air Control valve (IAC), Exhaust Gas Recirculation regulator (EGR) or the fuel pump and filter. I changed the intake plenum gaskets for around 40$ (with a military discount and an Autozone rewards card) that's a whole lot better than $1,000+ from a dealer. I hope this helps. Semper Fidelis!

 

you may have a leak around the tube going from EGR to intake. That's where mine was leaking before another leak had started. 2nd leak occured a few weeks later found to be lower intake gaskets