IAC valve
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Freshman User
Joined: Jul 2003
Posts: 43
Likes: 0
From: houston
IAC valve
i am having problems with the idle of my truck, when the ac is off it dips down to 300 rpms then bounces back to 500 then back down then back, does this sound like the IAC (idle air controller).
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
IAC valve
Hi Stoner150 and welcome to FTE 
It does sound like you could have a bad IAC. They dont cost too much and are easy to replace but before you do that you might want to check for vacuum leaks and maybe have your truck's PCM scanned for any trouble codes.
If you do a search here you'll find lots of info on vacuum leaks.
It does sound like you could have a bad IAC. They dont cost too much and are easy to replace but before you do that you might want to check for vacuum leaks and maybe have your truck's PCM scanned for any trouble codes.
If you do a search here you'll find lots of info on vacuum leaks.
Senior User
Joined: Jun 2003
Posts: 113
Likes: 0
From: Tulsa, OK
IAC valve
Sounds exactly like a IAC valve, or vacuum. Racerguy is a genius. But from what I have heard, IAC valve's rarely go out. They gunk up a little, but still work well. They are inexpensive, only 45 bucks at autozone, so that might be your first choice. Just like Racerguy said. Although, you can test your current one in two ways.
1) With the truck off, remove the electrical plug. Check the resistance of the terminals on the valve with an ohmmeter (multitester). It should be between 7 and 13 ohms. If not, that is probably the culprit.
2) With the truck and normal idle, unplug the electric from the valve, then plug it back it. From what I have learned, a truck should almost stall out or die when it loses the iac valve. You should at least notice a difference in the idle speed.
If neither one of those eliminates it as the problem, then I would go ahaed and replace it. Can't hurt anything, especially if your truck is higher in mileage. You can also try running some carb cleaner through it all. Might help a little. Definately take the valve off and look inside it. If it is all gunked up and black, then replace it.
But from what I have heard, IAC valve's rarely go out. They gunk up a little, but still work well. They are inexpensive, only 45 bucks at autozone, so that might be your first choice. Just like Racerguy said. Although, you can test your current one in two ways.1) With the truck off, remove the electrical plug. Check the resistance of the terminals on the valve with an ohmmeter (multitester). It should be between 7 and 13 ohms. If not, that is probably the culprit.
2) With the truck and normal idle, unplug the electric from the valve, then plug it back it. From what I have learned, a truck should almost stall out or die when it loses the iac valve. You should at least notice a difference in the idle speed.
If neither one of those eliminates it as the problem, then I would go ahaed and replace it. Can't hurt anything, especially if your truck is higher in mileage. You can also try running some carb cleaner through it all. Might help a little. Definately take the valve off and look inside it. If it is all gunked up and black, then replace it.
