Any Jeep Cherokee experts here? Low engine idle

[geeman237]

I have a year 2000 Jeep Cherokee 4.0 straight 6 (automatic). This week the idle started to play up. The car started fine and at cold idled at about 900rpm. Warmed up and the idle would drop to just about 500rpm. It should be around the 700-750rpm mark. Driving home from work today it was getting worse. Now on the driveway it starts but won't idle and cuts out. If you give it gas no problem, it revs up. Once in Drive and going its fine. But when you stop, the idle just slowly drops then will cut out.
I read that a bad battery with low juice will cause poor idle performance. Well I just had the battery replaced. Oh, I noticed that idling or trying at 500rpm the voltage gauge showed barley 12v, but with revs its back up to just under 14v.
The car has coil packs and fuel injection etc.
Mileage is 160k. These engines are normally pretty bullet proof. I am wondering if its some sort of bad sensor, maybe a throttle cable has stretched a bit? You only have to tweak the throttle open a bit and its fine.
Any thoughts before I take it to the dealer? (I have a low confidence in them properly troubleshooting it)
Thanks

[Egg Chaser]

Idle control valve?

[geeman237]

Good call. I did some googling on the subject and this was the main suspect. I bought a new one today from the dealer ($$$$ for a plunger thingy!) Relatively easy to fit and it may be the root cause of the problem. So far the idle has remainded steady at about 650-700rpm without stalling. Fingers crossed then.
I had to jump into my trusty XJS as back up today, which was nice.

Gordon

[Steve_D]

If you're a dirt under fingernails guy then you could try stripping and cleaning the old one.
This type of valve just gets dirty and gummed up so a clean may give you a working spare for the next time.
Cleaning this on an older Range Rover or Discovery is almost as frequent as topping up the screen wash.

Steve

[paintman]

Use a degreasing/carb cleaner spray.
With idle air controls (often referred to as stepper motors) DON'T be tempted to pull them about by hand as that will usually break them.