IAC steps.

[Big Kahuna]

I am having some issues with my IAT steps.
I was informed that mine should be around the 30 mark at idle when warm but Im seeing them average around the 7 mark and sometimes my TP is at 0.4 but mostly at 0.0.

What do I change (and perhaps by how much) to get my iat's to increase to the 30 figure as was suggested (by someone with far more experience than me)

Is it B4307??

[TAQuickness]

I'm assuming you ment IAC (Idle Air Control) instead of IAT (Intake Air Temperature).

In the case of IAC (on cable actuated TB's), the goal is really to give the valve enough room to control idle. IMO, 30 steps is a bit on the low side. Stock the IAC count is about 60 steps at hot idle.

An IAC count of 0 steps means the IAC valve is closed. A count of 310 steps is 100% open. In your case, 7 steps, the valve is almost closed, indicating too much air is getting past your TB at idle. To correct this, you will need to adjust the set screw to allow the TB blade to close more. If the set screw will not fix it's because the TB blade hole is too large, you may need to replace the blade and drill a smaller hole.

[TAQuickness]

FWIW, My hot idle is about 70 steps.

[Tordne]

Mine is around the 40 mark which is fine. Your's is way to low thought.

You may need to adjust the throttle body set screw (close the throttle I think). You will also need to do a TPS reset after that.

[TAQuickness]

Good catch. Forgot about the TPS reset.

[Tordne]

Changed Title of thread to IAC Steps :)

[Big Kahuna]

Yes definately IAC steps not IAT.
Sorry.As someone said b4 Brain fart.

Ill make sure the TB blade is closed fully, as the set screw can be adjusted further down.
Reset the TPS switch and then log to see IAC steps.

If its still low how do I increase the steps to something close to 30ish. Do I increase B4307?

[Tordne]

See how you go with the set screw before deciding what else might be required... The IAC steps can change quite a bit with small changes tot he set screw.

[Big Kahuna]

Yeah will do Andrew. I was just reading a couple of older posts regarding this very question.
Im onto it. :)

[Doc]

If you haven't already, do a search on RAFIG and RAFIPN which stands for running airflow in Gear / Park/Neutral

[TAQuickness]

Yes definately IAC steps not IAT.
Sorry.As someone said b4 Brain fart.

Ill make sure the TB blade is closed fully, as the set screw can be adjusted further down.
Reset the TPS switch and then log to see IAC steps.

If its still low how do I increase the steps to something close to 30ish. Do I increase B4307?

From an ealier post:


I'm assuming you ment IAC (Idle Air Control) instead of IAT (Intake Air Temperature).

In the case of IAC (on cable actuated TB's), the goal is really to give the valve enough room to control idle. IMO, 30 steps is a bit on the low side. Stock the IAC count is about 60 steps at hot idle.

An IAC count of 0 steps means the IAC valve is closed. A count of 310 steps is 100% open. In your case, 7 steps, the valve is almost closed, indicating too much air is getting past your TB at idle. To correct this, you will need to adjust the set screw to allow the TB blade to close more. If the set screw will not fix it's because the TB blade hole is too large, you may need to replace the blade and drill a smaller hole.

But, definately try the set screw first and go from there.

[Big Kahuna]

From an ealier post:



But, definately try the set screw first and go from there.

Ok after much screwing (pun intended) around with the throttle stop screw and some alterations to make the T/B blade hole smaller. I am still seeing the IAC steps around the 19-24 mark. As soon as the cooling fans kick in the steps go to 34ish, so Im making some progress.

Ive noticed that with my T/B screw adjusted fully closed, the steps decrease, if I open it slightly (1 turn) the steps increase which suggests to me that either the balde is past 45 degrees when fully closed and starting to open again, or the blade itself isnt of the best machine work.

I've gone from T/B blade hole size of 4.5mm down to 3mm. I'm going to close it fully this morning and do some more testing. Ive notice if I place my finger over the hole to close it off, my IAC steps are in the mid 30's.


What do I make of all this????????????????????????

[ringram]

You have a weird throttle body :D
But it sounds like you are on the right path

[Big Kahuna]

You have a weird throttle body :D
But it sounds like you are on the right path
Given the T/B is from STARR Performance, anyhting is possible. The king of rip off.
Ive had it for many years so I will persist with closing the hole up and if that sucks, then Ill refit my stock t/b and start all over again.

But to answer one of my question still unanswered. To increase the iat steps, do you increase the desired airflow table?

[Doc]

Sounds like you have answered your own question...The hole is letting in too much air. By the way, how are you "making" these holes smaller? My untouched 80mm BBK has no hole, my stock 75mm Fbody had a little hole. With full control of the IAC valve via the cal I don't think there is a real need for a hole for most applications.

[Big Kahuna]

Sounds like you have answered your own question...The hole is letting in too much air. By the way, how are you "making" these holes smaller? My untouched 80mm BBK has no hole, my stock 75mm Fbody had a little hole. With full control of the IAC valve via the cal I don't think there is a real need for a hole for most applications.
Thats intersting Doc. I didnt know the BBK's had no hole.

No hole it is then.

[Big Kahuna]

Well as my predictions and logging suggested. After filling the hole, the car idles magically at 850 with iac counts of 30-35.

Bout time. :)

[Rhino79]

Did you weld it up or what??

[eboggs_jkvl]

Did you weld it up or what??

I think it was chewing gum?:nixweiss:

Man, welcome to the club. I've twisted that damn set screw so much I have carpal tunnel! IAC is hell to get right.

[Big Kahuna]

Did you weld it up or what??
Bronzed close.

[joecar]

Bronzed close.Chewing gum activated by oxy-acetylene.

[bK]

Thats intersting Doc. I didnt know the BBK's had no hole.

No hole it is then.
This might help put some light on the matter from Dan at Chipmaster writes on another great little forum:

The Starr was designed to not need a hole unless you have a big cam.

If you have drilled the hole too large then remove the blade and solder the hole up , redrill to the size you need if any.

Idle is a mix of getting the air requirements right , the timing and fueling correct , once all parameters are met it will idle sweet.
from http://ls1-australia.com/forum/viewtopic.php?t=446&highlight=

[Doc]

Well bk, all I can attest to is I will admit to buying my bbk brand new from tybrne in 02- I know, I got spanked, I had no idea... and it has no hole even till this day. That IAC valve has quite bit of travel. I agree that with the right spark and fuel combo w/ des air right on there should be no need for a hole.

[Big Kahuna]

This might help put some light on the matter from Dan at Chipmaster writes on another forum:

from http://ls1-australia.com/forum/viewtopic.php?t=446&highlight=


Good find mate. Well done. :rockon:

Interesting that Ive had the T/B on 2 different cars now, both of which have been cammed.
First was back in 2001 and it was a crane 228/228 560 110. A cam I wouldnt classify as large by any means. When tuned (by a very reputable tuner) had the t/b drilled.

Second car is my current ride and it too was tuned initially by a different, respected tuner and he left it with the hole. My current cam is 222/224 570 112.

Interesting to note for sure.

After some more tinckering yesterday, I now have a really nice idle at 850, and an IAC count of 40. Fantastic!!!!