Quick Questions about IAC Control

[Aloicious]

Okay, so I'm trying to adjust my IAC and ran into some oddities. first off here's some info on the vehicle and conditions:
1996 chevy c1500 5.7L L31 running a 411 PCM, 75mm TB (stock is 72mm) with the TB blade deflector removed, ZZ4 cam, MPFI running Bosch 890 24# injectors. Tune is OLSD, tune attached below
IAC adjustments all done at temp (94*c) while idling.
RAFIG has been done several times and was stabilized around +- .20 in most cells from 20* up thru 94*, although the last time it was done was a few weeks ago. RAFPN hasn't been done as much, but was done about 2 weeks ago.

so after some adjustments I got the IAC steps in P/N at about 58-60 (before adjustment it was around 80-85), but in gear, the best I could get it at was around 103 (before adjustment it was around 130). my desired Idle in gear is set at 700, and in P/N its 770. I also reset the TPS afterwards to set it back to zero.

while adjusting the blade it started acting strange. I would get the in gear IAC steps down to 100 (started around 130), and either direction I would adjust the throttle screw the IAC steps would go up (opening or closing blade.) any ideas what's going on there? (IAC steps in P/n are more stable, I can take it down to about 43, it won't go any lower, but also doesn't go back up, so I'm guessing that is with the set screw all the way out.)

Okay, so in the other threads I've read, everyone says to get the IAC steps around 40-70 steps idling at temp. is that in gear, or in P/N? if it's in P/N It should be doing good, but is 100 steps in gear too high?

well, its about midnight here, so hopefully this thread makes some sense. thanks for any help out there.

[Aloicious]

still wondering about this if anyone knows.

[joecar]

I think 100 steps IG is just a little too high.

[5.7ute]

The way I understand the system(which could be wrong) is that the idle air trims will adjust according to the difference between commanded & actual idle speed. It is the average of these trims which gives you your desired airflow table in the rafig/rafpn process. Since the initial control of idle speed is made by spark corrections(since the iac valve is too slow to act) dialling in your idle spark should be done before rafig/rafpn.
Your higher count while in gear could possibly be lowered by getting the base spark in gear table dialled in a little better.
This is only a theory as I dont have an auto car to play with.

[Aloicious]

The way I understand the system(which could be wrong) is that the idle air trims will adjust according to the difference between commanded & actual idle speed. It is the average of these trims which gives you your desired airflow table in the rafig/rafpn process. Since the initial control of idle speed is made by spark corrections(since the iac valve is too slow to act) dialling in your idle spark should be done before rafig/rafpn.
Your higher count while in gear could possibly be lowered by getting the base spark in gear table dialled in a little better.
This is only a theory as I dont have an auto car to play with.

I believe you're on to something here. I did some more adjustments, but was only able to get the cound IG down to the mid 90's at best. but after altering the base spark IG a little it dropped down to around 82-83. Once I get teh base spark IG and P/N better I'll re-RAFIG/RAFPN as you suggested becuase now the IAC counts in P/N are pretty low (around 22).

Plus, since we're on the topic of base spark, I've just noticed that the spark readings in my logs are for the most part very smooth while driving and in p/n, transitions are relatively smooth and minimal jumping around. but the spark while idling IG is kinda erratic, it averages around 22*, but contantly is jumping from anywhere around 19* up to 28*. I've also noticed this erratic spark behavior also effects the AFR at idle. AFR swings are much larger at idle IG than elsewhere.

Is there any generally accepted methood to altering base spark other than trial and error?

[5.7ute]

The easiest way is to use the BIDI controls delta spark function. You should be able to add or remove spark with this to find the sweet spot, then modify the base spark table to what you find the engine likes.

[Aloicious]

The easiest way is to use the BIDI controls delta spark function. You should be able to add or remove spark with this to find the sweet spot, then modify the base spark table to what you find the engine likes.

nice, I'll try that out and see what she does. Thanks.