Need help with IAC settings

[SV8346]

Ok, this is the first time i have needed to alter the IAC settings and i'm not sure whats what. I have put a larger billet throttle body on and now i have a few problems.

When i give it a rev in neutral(manual) revs rise very quickly now but then when returning to idle it drops way to low and struggles to recover itself.

When i go for a drive, if i come to a slow stop and put it into neutral at around 1500rpm the idle hangs at around 1200rpm and takes about 20 seconds to return to normal idle of 750rpm

[Tordne]

Is the IAC steps the ONLY thing you changed?

That kind of sounds like Throttle Follow decay delay.

[SV8346]

at this stage i havent changed anything in the program relating to idle or throttle follower, i have looked through all the setting but wasnt overly sure what each one does so thats when i thought i'de come and ask on here first.

[Tordne]

What size TB did you fit, and what brand?

Is the IAC steps table still stock, or have you tried the GTS table?

[SV8346]

its an 80mm throttle body from CRT performance, does the throttle body blade need to be set to a specific setting?

the only setting i have noticed that is different from the GTS settings is B4403, IAC Effective area. The GTS peaks at 140 steps where as mine is set to peak at 310 steps

[Tordne]

Does the throttle blade have a small hole in the face?

If you use the GTS settings you'll find that the car will likely stumble and almost stall when coming to a stop. So, I'd probably leave the stock settings for IAC effective area alone. I have a 78mm and stock settings.

[SV8346]

there is no hole in the face of the blade

[Tordne]

Check out some of these threads:

- http://forum.efilive.com/showthread.php?t=7154
- http://forum.efilive.com/showthread.php?t=4237
- http://forum.efilive.com/showthread.php?t=4219
- http://forum.efilive.com/showthread.php?t=3568

There is heaps of info on all this stuff on this forum. Search for things like 'IAC Steps', 'Throttle Follower', Throttle Cracker' etc.

Cheers,

[SV8346]

thanks mate, i have played around with the throttle stop point and doing TPS resets and now have the IAC steps floating around 38-39 during running temp idle. Idle also sounds allot quieter now, doesnt seem like its sucking as much air threw the IAC port. When i first check the IAC steps it was at around the 200 area so i opened up the throttle with the stop screw.

Is what i have done correct?

[Tordne]

Pretty much spot on what mine is like - ~ 40 IAC steps at warm idle. The reason for having it something like that is that the IAC can react faster to changes. For example 40->60 IAC steps is an increase of 50%, whereas 200->220 IAC steps is only 10%.

The rest of your solution will be in doing the RAFIG process. If required after this you can look at Throttle Follower and Cracker settings to refine.

[SV8346]

sorry Tordne not much up to date with all the lingo, Whats RAFIG? mean.

[ScarabEpic22]

Im not either, but I think its Running Airflow In Gear and RAFIP is Running Airflow in Park... Dont have these for my truck, they're ETC.

[Tordne]

RAFIG is a process for tuning the Desired Airflow table (B4307). This table will cause the car to hold a high idle or to stumble and almost stall.

Have a look at this thread: http://forum.efilive.com/showpost.php?p=45554&postcount=4

[SV8346]

ok i have done the RAFIG and it came out that all squares were out by roughly -0.1. Is this good or bad?

[Tordne]

It's good assuming the correct PIDs were used. You mind sending the log to support@efilive.com?

[SV8346]

i havent got the log on this computer its on the laptop, the Pids i selected were, GM.IAC_LTD_DMA, GM.IAC_STD_DMA, CALC.RAFIG, GM.DYNAIR, SAE.ECT and all the other standard metric pids.