So I Finally Fixed My Idle

how much is the kit?
yeah i have the same problem but i havent really tried a whole lot other than cleaning the TB.

that is listed in the FAQ thread by JRichker at the top of the forum. Thanks for posting feedback that it worked.

Mine has lost the high idle. When you start it and it idles high then lowers itself automatically. What causes that? It starts like my old '67 did. When it's cold, I have to give it gas to keep it running.

DouglasOhio said:

how much is the kit?
yeah i have the same problem but i havent really tried a whole lot other than cleaning the TB.

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I was gonna buy one from 50resto.com, but I found the part number and called my local ford dealer and am actually going to get mine in a few minutes. It's called the Engine Idle Air Kit part number F2PZ-9F939-A. It's around $30-35. It's around $32 at 50resto with shipping.

Those of you about to spend $35 -- just know that it doesn't always work. The only way to find out is to try it.

What exactly are you talking about???

I looked at 5.0 Resto and in my FRPP catalog and I don't follow...

Michael Yount said:

Those of you about to spend $35 -- just know that it doesn't always work. The only way to find out is to try it.

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Hoping I'm one of the lucky ones that it works for. Worth the $35 to try if you ask me. Otherwise, my car will basically be a big paper weight; I can't drive it if it's gonna surge every time I stop and be a head ache.

On a side note, I just picked up the unit and it says "Do not clean the throttle bore/plate area. Removing sludge accumulation in the throttle bore will reduce the effectiveness of the idle air adjust spacer."


Here it is at 50resto.com 1986-93 Idle Air Control Adjuster
Item #LRS-9939A

The reason for that warning is because the idle air adjust plate was originally developed by Ford as an emissions recall item. Ford were having problems with vehicles that had - you guessed it - hunting/surging idles. Ultimately throttle bodies and/or IAB solenoids should've been cleaned or replaced. But Ford found a much cheaper fix - a $20 (that's how much mine was 3 years ago from the dealer - they're hard to find now) bolt on piece that allowed more air to bypass what was usually a partially clogged IAB solenoid. Ford found it was MUCH cheaper for parts and labor to simply bolt on the bypass plate.

So now you know what it was designed for - and why if often doesn't work on our idle problems. They are usually a result of mods made to the engine that the ecu isn't quite sure how to respond to. It's the computer that's designed to control idle speed to 675-700 rpm. And when it can't do that (because of more radical cams for example, or mis-calibrated maf's) it tends to surge trying to find a happy rpm level. Adding the plate often only results in the IAB solenoid doing the same cycling that was causing the surge in the first place, but a bit more closed than it was before the plate -- because the plate is allowing some of the idle air needed to bypass the throttle plate directly.

Good luck with it. I ultimately pulled mine off and sold it to someone else - who probably sold it to someone else.....

Now I follow....

I've heard that speed density cars can be made to idle with better heads and a cam with these controlled air leak plates. Any truth to that?

I would imagine that the 'air leak plate' (I like that term) was actually developed with the speed density cars in mind. They would've been the first efi cars that started having the high miles/dirty components/idle surge issues. But that's just a logical deduction on my part.