I am tuning my 730 ECM right now, and I have been told I have too many IAC steps. What are they, and what should they be at? How do I change them? Thanks in advance.

 

why do you hae to many steps ?? the only situation ive seen where reducing IAC steps is handy is with the truck TBI ecms. idle surging ?

 

A step could be thought as a short voltage pulse to a dc motor, causing the motor to turn a know amount. Which intern truns a pintle which covers an orfice, so more steps means more retraction, which means more air bypassing the throttle blades and going through the orfice into the intake.

I shoot for about 5 iac steps when my motor is up to temp. Any more and you get ugly fuel atomization when the throttle blades are closed.

 

When you say that you "shoot for about 5 iac steps when my motor is up to temp", how are you exactly getting this? By adjusting the VE tables and main SA table? I'm running a 383 with a 454 TB and 90lb/hr injectors on a 7747 and I'm getting way to many IAC steps when my engine gets up to temp. It's causing a very lean condition and makes my engine die. AFAIK, the "IAC Steps vs Coolant Temp" table times out and is no longer used when the engine warms up. So how can I reduce these IAC steps?

 

First you need to set the min idle speed. And you want to double check and make sure you have the initial timing right.

The hot idle IAC steps are *set* thur mechanical means.

In quick summary.
Engine at temp.
Short A->B at the ALDL
Key on
wait a min, and unplug IAC
Key off
remove A->B jumper.
Start engine.
Set min idle speed, typically ~650 RPM
Set timing.
Key off
reconnect IAC, and EST if you set the timing
Start engine, and test drive.
Some codes have to *see* 35 MPH to reset the IAC.

Now see what your IAC count is after test drive.

 

Yeah!! Like grumpy said.


And if your like most people here you'll grow to really hate the little IAC bastard!

 

i will be adjusting the iac steps when my 454 TB install comes in spring. i read in this post that some steps(5) is warrented at warm idle. i was going to use my current dual single TB steps as a benchmark and just double what is in my current chip as a start. explain please. it appears 5 steps would allow some air flow past the pindle? that plus the current throttle stop setting should put me in ball park. so the idle air requirement is possibly coming from both the butterfly gap and also the iac pindle position? is the fact of the idle stop screw preset(new unit) for a 454 application possibly set to great for a 350 cid and will need to be closed up a bit. my warm idle is set in ecu to 650 rpms.