Fluctuating Idle UPDATE

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Apr 22, 2010 | 10:04 AM

kawa

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Joined: Jun 2007

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From: Rogue River, OR

Fluctuating Idle UPDATE

Several months ago and up to the other day my "98 4.0 Ranger has been plagued with this idle surge coupled with the A/C cutting on and off.

https://www.ford-trucks.com/forums/9...ating-idle.htm.

Paw Paw gave me some great fix-it advice but that only lasted as a short fix. I finally bit the bullet and bought a new IAC valve all to no avail, problem still existed.

I once again cleaned the old valve with plastic safe cleaner but this time I removed the vent cap, cleaned both vent filters. I once again dried everything with low pressure air and reassembled the valve and re-installed it on the engine.

Now, the mounting pad on the engine has an "O-Ring" laying in a groove and in the past I had always relied on this to act as a sealing gasket by lightly coating it with grease before re-assembly.

This time I installed a paper gasket on top of the O-Ring, re-installed the freshly cleaned IAC valve and VIOLA! Fluctuating idle is gone and has been for several hundred miles.

Your guess is as good as mine as to what the actual cure was but for my money it was the "Gasket". I'm not going to dis-assemble it to remove the gasket to test my theory, I'm just too happy hat the fluctuation is gone.

Rog

Apr 22, 2010 | 10:25 AM

Rockledge

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Joined: Jan 2003

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From: Connecticut

I know that O-ring gasket that you are talking about, it's kind of flimsy. It reminds me of the stringy upper intake gaskets, which also fit into grooves.

(Some aftermarket IACs come with a different style gasket, BTW).

Good feedback, hopefully you solved the issue for good. If so, it might be worthwhile for people with similar issues to try a new gasket before changing out the IAC.

Apr 23, 2010 | 07:56 AM

pawpaw

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Joined: Jan 2004

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From: SW Va

Good feedback on your IAC problems.

Interesting theory about the IAC "O" ring seal, as I too have wonderd about the oem seal taking a "set" & flat spotting & maybe not sealing well.

My new IAC came with a flat paper gasket & I too installed it over the OEM "O" ring seal.

I still have my oem IAC, that I could never find a visual problem with, so I'm of a mind to go break it out & do a step by step recleaning, including the "vent filter" under the little black cap, which I never removed to clean & see if my oem IAC will revive & if not then use the paper gasket on it & see what happens!!!!!