Ok, i have tuned my chip last year for my TBI camaro. It idles just a tad high, now can i use the idle adjustment screw to tone it down a hair, or will it mess up the read out from the TPS and screw up everything, or do i need to do something in the chip to tone ir down like maybe a couple hundred RPMs, Any idea.

 

what are your IAC counts at idle? consider dropping them to 0-5 or so. I am at 0 counts. I assume your idle rpm is commanded to what you want and it is showing high. possible vac leak? i did use the idle adjust screw to drop the idle so that the plate was closed as much as could be. that was done since my IAC i believe was not functioning at that time and not fully seated.

 

where do i drop my IAC counts? Is it manually adjusting it, or dropping the counts on the chip, thanks! And what is it called if its in the chip?

 

There is a table in the chip that is labeled as "desired idle speed". Set this for your desired idle.

What the ECM will do is move the IAC open and shut (0 counts = closed, 255 counts = all the way open) to reach your desired idle speed. By "setting" your IAC to zero you open the throttle blades manually untill your counts get as close to 0 as possible. If the IAC counts just sit at 0 then the throttle stop is now controling the idle and you need to open it up a bit so the IAC can move around and control the idle.

The reason we like to get as close to 0 counts as possible is that it keeps the ECM from accidentally pulling too many IAC counts out and stalling the motor. More importantly at idle you want as much air as possible going through the TB so that it can atomize the fuel. Fuel atomization is the one downside of TBI, when compared to a MPI setup and anything you can do to help will make a difference.

 

i think it is IAC idle speed drive and another for neutral to command idle rpm vs coolant table. and IAC idle minimum steps(i see mine is 4).

 

Ok here are some of my tables, the first one on the left is IAC- Steps vs Engine temp, the next one over is IAC-max steps, and the column on the right is, Idle- target RPM AC off, next one down is Idle-target RPM AC on, next one down is Idle- Maximum Hot RPMs , and the last one is, Idle- Maxiumum Cold RPMs.

So do i need to change one of these tables or values, can i change the idle when cold to match the other RPMs under the Idle tables? Thanks just trying to figure out some of this IAC count and idle stuff. Thanks again!

 

The target RPM constants are the ones you want to change, with and without A/C is pretty self explanatory. The IAC counts Vs. Temp table is what the ECM uses to startup your vehicle. So if you are at 198 deg, the IAC is set to 64 counts untill the self learn kicks and in and tries to maintain 700 rpm. The other tables are just limiters and modifiers that keep your IAC from going to wacky.

Just jump in there and start changing stuff and see what it does. No real way to hurt your engine here.

 

Thanks, illl give it a try

 

definitely requires chip adjustment (with my experience anyway)

 

xjcamaro89, why do you have your IAC max steps set to 50? Just curious.

 

Thats just what it was set at from the beginning. I never adjusted to IAC steps, what number would be a better set of steps do you think?

 

I have my Max IAC Steps set to 160. My thinking is that when you get on the throttle you want as much air as possible flowing past the IAC.

 

You've got a 5speed so, stock bin is the AXKW which has Max IAC steps at 191 stock.

What does your engine idle at and where do you want it to idle?

 

It idles at about 800-1000 RPM, i would like it to idle at about 500.

 

Well, 500 is a bit low in my opinion, but just command whatever you want it to idle at in the idle a/c off table. Then datalog it idling and see what your IAC steps are.