Low RPMs and CEL

[psmith]

For the past couple days, whenever I start my 2000 Mountainer V8 I'm getting very low RPMs (~300) and the check engine light is on. This happened a couple weeks ago, but the problem went away pretty quickly. Now that the weather has turned colder, it seems like the problem is here to stay.

So... is the battery getting ready to die, or is this more likely a problem with one of the sensors/valves?

 

[03ExplorerSPT]

My guess is the IAC valve. If you do a search for IAC valve you should come up with tons of info.

 

[psmith]

If it's the IAC, should I replace it or just try to clean it? I've also had a whistling sound at start-up in the past, and now I'm wondering it that is also related to the IAC (Incidentally, the whistling seems to have gone away now that I'm having these RPM issues.)