HOW TO: modify a Termi IAC valve for single blade throttle bodies

[hookandpull]

Okay... I have been having the hardest time getting my new Accufab Single Blade Throttle body to work with any plenum I have because of my IAC (idle air control) valve. What is the problem you may ask? The simple fact that the IAC valve is what the ECU uses to measure 2 static pressures... Static pressure #1 is static air from before the Throttle body but after the Mass Air Flow sensor. Static pressure #2 is static air after the throttle body but on the vacuum side of the plenum (non boost). Static pressure #2 after the throttle body ultimately controls the valve but air needs to move freely across the plunger (the bridge in the IAC that connects static #1 to #2) in the IAC. The problem with Single Blade throttle bodies that I have found is that unless you buy the matching plenum to that throttle body your car will never idle or run right because IAC static port #1 is either blocked or is actually getting pitot pressure (direct air) forcing the plunger shut. I picked up an accufab throttle body that doesnt have a static port so it just blocks off the MAF static air thus canceling out the vacuum needed to operate the IAC valve. I could do one of two things... Buy a power plenum = hundreds of dollars or buy the MMR remote IAC adapter (which doesnt come with a IAC block off plate for the original location of the IAC on the plenum) not to mention they are on back order with a wait time of a several months.

So I took matters into my own hands and got a few parts and tools together listed below:

-1/2" Drill
-1/8 drill bit (actually one size smaller)
-1/8 pipe threaded brass vacuum fitting (Vato Zone)
-2' of 5/16 vacuum line or fuel line
-ultra black gasket maker
-1/8 pipe thread tap set

I decided to drill about an 1/8" hole into the MAF to throttle body side of the IAC valve lets calls this "static #1" I then tapped it with 1/8 pipe thread. I cleaned out the IAC thoroughly and let it dry. I then installed my new billet flow plenum and Accufab SBTB. I placed a dab of ultra black rtv on the threads of the brass fitting and threaded it into the IAC until good n tight. I installed the IAC onto the billet flow plenum and bypassed the Throttle Body by attaching my 5/16 vacuum line to my new fabbed brass fitting on the IAC and attached the other end of the 5/16 vacuum line to the vacuum port on my intake tube after the MAF. I started the car up and it ran great. The throttle response greatly improved and my idle was around 900 or less.

You can see the throttle body side of this Billet flow plenum has the slot cut out for a before throttle body static air input, but you will see that unless you have a billetflow TB which are hard to find and $450 your IAC will not work.

Again you can see that there is no static port on the throttle body where it mounts to the plenum

Here is the side view of my IAC valve after I drilled and tapped it... To the left you see the brass vacuum fitting

The underneath side of the IAC giving you a picture of how it works

IAC valve with new vacuum fitting installed

this is everything completed and working

Its not the prettiest but I am a function over form kind of guy with little patience and I hate wasting money when I dont need to. If you can get past the aesthetics its a great and cheap fix to an otherwise expensive and drawn out problem.

 

[01cobravortech]

This is bizarre...

 

[hookandpull]

Yeah I came up with the idea about 5 hours ago after getting off the phone with MMR and them telling me I couldnt order a remote adapter plate. I was tired of not being able to utilize my accufab single blade.

 

[hookandpull]

So been driving it with no problems today. Not completely sold on the Accufab throttle body yet. The pedal feel is way too light for my taste, and my car has been idling around 1k but I need to adjust the throttle body set screw and I should be golden.

 

[01bluesnake]

This is bizarre...

x2 yes

To the OP, Someone didnt fill the IAC opening on the TB did they? Dont think i have ever had to do this for a single blade TB setup and i have installed a few Accufab single's. As far as im aware, both BF and Accufab have IAC air provisions, unless you are using the wrong TB. You sure you didnt get a lightning throttle body?

 

[hookandpull]

there was no opening on the Accufab throttle body whatsoever.

 

[01bluesnake]

Ok, then im almost positive you have a lightning T body. The lightning uses the IAC on the side of the plenum with a remote source vs taking air through the blade area on the 03/04 .

 

[hookandpull]

Well regardless I got it to work now lol. I am sure this method would work if you want to cut your stock plenum to fit a single blade as well.

 

[timbo3282]

For Gods sake please don't call it a Termi. Its a muscle car not a Muppet.

 

[timbo3282]

x2 yes

To the OP, Someone didnt fill the IAC opening on the TB did they? Dont think i have ever had to do this for a single blade TB setup and i have installed a few Accufab single's. As far as im aware, both BF and Accufab have IAC air provisions, unless you are using the wrong TB. You sure you didnt get a lightning throttle body?

x3

My Accufab works perfectly and I didn't modify a thing.

 

[10thSVT_03]

So where does the other end of the vacuum hose attach to?

 

[hookandpull]

For Gods sake please don't call it a Termi. Its a muscle car not a Muppet.

Troll someone elses thread thank you

 

[hookandpull]

So where does the other end of the vacuum hose attach to?

It attaches to the intake tube between the MAF and TB. As you can see in my pictures that my TB has not been machined for an IAC valve hence why I went this route. It cost me $2 and about 45 mins if that. I am sure this method will work for people that want to retrofit a single blade to a stock plenum. Even if you end up with the right single blade that has been machined for an IAC valve it wont match up to the port on the stock plenum. That is a known issue for sure, and my method will allow you to still utilize the combo at little cost to you.

 

[hookandpull]

x3

My Accufab works perfectly and I didn't modify a thing.

Do you see this picture? can you see where there has been a port for your IAC valve to measure forward throttle body static air? There is no port on this throttle body and rather than buying a new TB for God knows how much I decided to fabricate a solution out of shit in my garage. I am an engineer by trade and was actually curious to how well this solution would work. Maybe I should change the title of this thread to make it more useful for those doing non standard applications.

 

[RacerXHG]

That was a good work around! They're just thrown that you had to do that because a 03/04 Terminator Accufab SBTB does have the slit. The IAC doesn't take any measurements btw. It's simply a little motor that controls the opening size and the amount of air to keep the engine within the the idle guidlines set in the PCM. Done by RPM. As long as it's only drawing in MAF measured air pre-TB, not a prob. Your idle may actually settle down over time as long as the blade is shut. BTW, that plenum looks SHINY! Who polished that??? :coolman: Oh yeah, you could throw another light spring on the TB for more return strength. :beer:

 

[hookandpull]

Yeah I realize the throttle body is a motor. Being an engineer when I see something that Has linear variable return voltages I automatically think of a motor transducer which can be a sensor in certain applications, because manifold pressure/ vacuum does effect the actuation of the IAC plunger. Yeah I wonder who polished that Plenum wink wink, but where can you get this spring you speak of?

 

[Blueline]

You can put a spring from the throttle linkage back to the throttle cable plate on the blower. If will make the pedal feel a bit better. I had the same issue, I bought a used Accufab for my 04 Cobra and I noticed when I put the gasket on there was no slit in the TB to match the gasket. I called Accufab and they told me that TB was actually for a 96-98 cobra. I bought another one for 03-04 Cobra and the IAC slit is there. I dont use the extra spring on my Accufab, I actually like the pedal feel.

 

[mmustangsrus]

hope i dont get fussed at by the mods for bumping this thread !!!

this will cure the hanging idle issues right ??

but has anybody had luck doing this with a dragon tb & plenum ??

considering where dragon moves the iac motor to the bottom side

 

[Willie2]

this will cure the hanging idle issues right ??

Ditto....which i assume is my 1058(i think) code....Idle air control over limit error

 

[hookandpull]

I am currently using it on my dragon Throttlebody posi ported inlet on my whipple. Seems to be working fine so far. This is basically just a poor mans 99GT IAC thats smaller