Hi there,
My Kia C'eed has had this problem with idling smoothly for years, and I only just noticed it a few weeks ago. At first, I attributed it to the bitterly cold mornings, but now that the mercury is higher, I can't get it to rev up to idle smoothly.
Occasionally, it sounds normal again, but like I mentioned, it's the exception these days; to help it along, I have to rev it up a bit to prevent that rough idling.
One of the sensors on my diagnostic machine read 108C, which is obviously wrong when I start the car from a cold start. Maybe this is the root of the problem. I tried turning off all the visible and accessible sensors to see if their live data would go awry, but none of the three did manage to alter the 108C. "Exhaust gas temperature valve pre particulate filter" is the name of the sensor to which you may be referring. Is this one plugged in but hidden from view?
If you have any suggestions on where I might look for the issue, I would be eternally grateful.
Just so you know, the MAF sensor is one of the most blatantly responsible parts of this. I took it apart to clean it with the right stuff, but it's designed so that we can't get a spray nozzle near it; I prayed it would do the trick, but alas, it didn't.