Q:

Automatic: revs dropping then stalling when stopped at lights

Kia Sedona 2012 automatic. Drove 180 miles on a full tank of fuel without any problems. Started the car the next day and it didn't start cleanly but did eventually. Was waiting on the drive with the engine running but in park when it suddenly stalled. Turned off all the accessories (air con, radio), started again messily, put into reverse to back out of the level drive without using the gas pedal and it stalled while backing up. Started again, drove down the road, got to the stop sign, stalled again.
Went away for a few days, came back, tried it again. Messy to start. Car hovers at 900rpm when idling and every 10-20 seconds the revs would slowly drop to about 500rpm before kicking back up to 1000 then back to 900. Every now and again it wouldn't recover from the drop and would stall instead, several lights on the dashboard lit up telling me nothing.
I think the battery is okay as the power doors operate fine. Driving at 55mph it's fine. It's only when idling that the revs drop and it (sometimes) stalls, plus starting takes a few seconds. Weather hot and dry, 30% humidity which is a little high for the region, no rain for ages (SoCal). Don't think it's fuel contamination as the 1st half of the tank ran fine.
Any ideas I can try as a non-mechanic before spending $$$ at the dealership? Thanks.

A:

Sounds to me like the IAC valve (Idle Air Control Valve) needs to be replaced. It's not a hard thing to replace. The IAC opens and closes to allow air into the throttle body when the throttle blade(s) are closed (which is at idle). It might be dirty or have debris lodged in it which is causing it to act up. I've been able to replace them on older 2005 vehicles for $20 from AutoZone, but I recommend getting a good one from the dealer (a little more expensive). If you want, you can also try cleaning the valve before replacing it.
A malfunctioning IAC will also cause the car to idle very rough or stall when the AC is on even if the car is fine with the AC off. 
If that's not the issue then it may be the ETC (Electronic Throttle Control) which is used in drive-by-wire systems in place of physical throttle linkage. If that's the case though, you would usually get a CEL (check engine light). 

