IAC Parameters

[DPS]

I'm having a difficult time getting a car to start and idle properly. One thing that I noticed is that {B4350} Max Desired Idle Area is set to 84 sq mm. Does this value limit the number of IAC Steps possible in {B4403}?

The car is a 383 LT1 with a 0411 PCM swap. I've been through this thread many times: http://forum.efilive.com/showthread.php?4661-Idle-Tuning-Helpful-Info-Inside
I have adjusted the TB and reset the TPS in order to get ~50 steps at warm idle before attempting RAFIG.

The results that I've had are not very repeatable. Sometimes it will die when coming to a stop and other times it will have the cruise control effect and high idle. Warm restart has been horrible too. I've made drastic changes to {B4343} Startup Friction Airflow Correction without any luck. I still have to play with the throttle to get it started.

Another concern that I have is the fact that it's an LT1. I'm unsure if the IAC is different and therefore the PCM isn't lining up with it.

Tunes and logs are a little scarce as I am in China for work and they are on my other laptop. I'm just trying to get ideas as I lay around at the hotel. :book:

[Taz]

Hello DPS,

Your comments regarding being in China on business, but your mind turning to automotive projects during down time, made me chuckle - that’s pretty much been my life !

OK …. I take it this is an “EFI Connection” type swap - LS1-B PCM, 24x CKP, LSx style coil packs, etc. ?

Regarding your question about the “physical” interface of the throttle body with your new controller, the good folks at EFI Connection may be able to help with that. As you probably know, they have posted “base” tunes, compatible with their conversion (cylinder banks reassigned), on their website for download.

The link to the EFILive Forum thread you posted is one of the best I've found for idle issues - I printed it out a while ago, and it now has that well used look !

It might be helpful to post the specifications / modifications to your engine, as well as your current tune.

Idle tuning of highly modified engines, is not a particular area of expertise for me - I do them one at a time, and it often takes many tries to get it right.

There are Forum members - WeathermanShawn, Joecar, and many more, that will probably be able to provide direct feedback regarding your specific situation.

Enjoy China …….


Regards,
Taz

[WeathermanShawn]

Less familiar with the LT1 and TB.

But, I usually avoid direct manipulation of the TB for Idle adjustments. I also have followed the Idle Tutorial to a tee.

Nevertheless, in this order I usually ask my self the following questions.

1. Fueling: What desired Idle AFR do I want..and what Idle AFR am I actually getting?
2. Spark: What Base Spark do I want, and what am I getting?
3. Airflow: What Desired Airflow do I want, and what am I getting?

Most Tuners make the following mistakes.

1. Too much Idle Fueling..
2. Not enough Base Spark for Idle
3. Not enough Desired Airflow.

Those steps are it. You should not have to adjust the TB. The Tuning software allows a more predictable way of making adjustments. It could be the nature of your particular TB.

Those are my thoughts. Good luck..

[DPS]

Thanks guys. The car is indeed another EFI Connections swap. This is the second one that I've tuned. The first was just an LT1 with a hotcam and bolt-ons. I never saw these issues with that car.

The thought process behind adjusting the TB was to make sure that the IAC had to work a little @ idle since the IAC can't remove air.

I believe the car is currently running ~25* of base spark. I could try to bump that up a little. I also targeted 13.5:1 AFR @ idle when tuning the VE. I suppose it's worth it to check it again. I was under the understanding that this was a decent target for cammed cars to combat surging.

Thanks again. I'll go back through the basics one more time.

:cheers: