Replacing the IAC Valve

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Dec 4, 2005 | 06:10 AM

ghkramer

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Joined: Nov 2005

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Replacing the IAC Valve

I’ve been having a problem starting my 99 F-350 V10 in the morning. It seems to fit the classic IAC diagnosis: lightly press on the accelerator and it will start (the sputters a couple of seconds at ignition and then rev’s up but with no need to continue pressing on the accelerator). This only occurs in the morning. I have NO idle or stalling problems.

After searching this forum I decided to replace the IAC valve. The procedure as described in the shop manual is

Disconnect the battery ground cable
Disconnect the electrical connector to the IAC valve
Disconnect the throttle bypass hose to the IAC valve
Remove the two bolts and washers, and discard the gasket
Reverse the procedure for installation

As stated many times in the forum there is a limited space around the IAC valve, but removal and installation is possible. I explored the area around the IAC valve and have a few questions about the replacement process:

It appears that disconnecting the power brake booster vacuum supply hose and the main vacuum supply line from the throttle body would provide easier access to the IAC. Is this recommended?
I tried to pull off throttle bypass hose from the IAC valve but it’s on very tight with little room to get any leverage. Any suggestions?

Thanks in advance.

Dec 5, 2005 | 12:58 AM

cfd29

Senior User

Joined: Jul 2004

Posts: 198

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From: Arkansas

I have had the same problem with my 99 V-10, but did not replace the valve, just remove it, clean it very good, use some good cleaner and a tooth brush and get all the carbon off it, until it is clean and shiney inside and works smoothly, then just replace it, no cost except for your time. I have had to do it twice now on mine since I bought it new in 1998, last time took me about an hour, the bottom bolt is something else, but it is not too bad a job..
as far as the bypass hose, the first time I took it off from the other end from the valve and removed valve with the hose still attached, then I could work the hose off gently after it was out and away from everything, it is much easier and then easy to replace the hose when you get the valve mounted back again..