Stalling IAC goes to 0 only after revving stationary

[HoldenTuner]

Ive been chasing this issue for weeks, If I rev the car above idle for 5 - 10 seconds it will always run the IAC down to zero, and will either stall or have a near stall experience once I get off the throttle. Ive checked the TPS, and Ive put back ALL the stock settings in the Idle/RPM and Idle/Airflow tabs in hptuners, with the same result. Hot or cold same result also.
If I do the same revving while rolling at any speed, this problem does not happen at all, so It does suggest its not a sensor but might be in the Adaptive Idle Airflow section since it only kicks in when stationary as I understand it. Though like I said Ive put these back to stock. I realise I can drill out the throttle valve, or adjust it to be slightly open, but this dosnt fix the problem, since the minimum airflow will then be correct for either hot run or cold run, but not both, also Im trying to learn as much as I can rather than sweeping it under the carpet.

The car is running a medium cam, mafless config, manual trans. Hot or cold same results.

Attached log and pics. Log shows normal idling, then holding throttle to get 1800rpm or so for about 9 seconds, meanwhile you can see the IAC drops to zero, then I catch it from stalling with some small throttle blips while the IAC re settles itself.

Can someone suggest a setting to try, or can this still be another sensor I need to test?

IAC-2.jpg HPTuners set AIA.png

[anniversaryss]

tune file?

[HoldenTuner]

Added tune file

[anniversaryss]

I feel like somthing is decaying causing your IAC to close up.

I would try by logging all of your idle parmameters like STIT, LTIT, Throttle followe, throttle cracker etc. Any idle airflows.

I feel like its somthing to do with throttle follower but i am not sure.

[HoldenTuner]

anniversaryss, Ive got all that were available you mentioned except Idle Follower AF, I can do another run tomorrow and get that one if you think its needed.
(note STIT doesnt seem to exist in this ECU.)
2 logs attached,
- the rolling test I hold throttle while rolling at 2:12 till 2:18 and there is no effect on the IAC position, normal idle follows.
- the stationary test at 6sec mark I hold down the throttle, and it stalls after I get off the throttle

seems like the LTIT's and throttle cracker didnt move when I did the stationary run

Anyway, let me know what you think.

[HoldenTuner]

I think were onto something now.
Found the STIT and the Idle Follower Airflow and added them both (ps the search feature in HPtuners doesnt find "STIT" had to find "Idle Adapt")


So now I can see the Idle Adapt STIT drops from -5.0 to -10.3 while doing the revving, so this must be a big clue, to what Im not sure.?
p.s. I also re-uploaded the full map just in case I had corruption in the data, then keyed off the car for over a minute before this test.

STIT Idle Adapt added Screenshot_1.jpg

[HoldenTuner]

Ive adjusted a couple of the settings, ST Adapt Airflow Max from ~3 upto 9.3g/s at operating temp, and Idle Base Running Airflow down to a more reasonable 10.1g/s
it seems that revving above about 2400rpm will defeat this problem, and the IAC will go back upto a normal idle value >100.
So in other words this problem only happens if I rev the motor in between 1000rpm and around 2200rpm for 5 to 10 seconds. FIIK what can cause this.

Theory of mine: Its almost asif the ECU thinks we're still in idle when I clearly have a throttle position of about 6 - 10% and starts to lower the IAC to compensate.

Attached another log file playing with throttle pedal to get different revs and watching the IAC position do unexplained different stuff at different revs.
Image showing edited Idle Airflow values.
IAAFM-IAFCT.png

[lukearmstrong1990]

Try disabling rolling idle

Set cracker to 5&7km/h enable disable

And get the car idling warm on 13-15 degrees

You may need to set the throttle blade to a greater angle and reset the0% to mechanically add more air.

[HoldenTuner]

lukearmstrong1990
Ill give that a try,
do you mean disabling Rolling Idle by setting the Idle/RPM/Rolling Moving Idle all to zero? or do you mean setting some parameter in the Idle/Airflow/Rolling Idle to disable or zero, they are in 2 different tabs and Im not clear if they are related or are applied under different circumstances.

[HoldenTuner]

Try disabling rolling idle

Set cracker to 5&7km/h enable disable

And get the car idling warm on 13-15 degrees

You may need to set the throttle blade to a greater angle and reset the0% to mechanically add more air.

Anyway I disabled both parts of the rolling idle by setting:
- Rolling Moving Idle all to zero, and setting rolling idle to 411kmh, 411kmh.
- set the cracker to 5 & 7 as you suggested
- Idle advance warm actual is 11-15 degrees

similar result, revving the engine between 1000 - 2400rpm results in eventual IAC going to 0, let off the throttle stalls, added log files showing 3 examples,
01) Cold idle rev over 1000rpm = stall
03) Warm idle rev over 1000rpm = stall
04) Warm idle rev between 1000 - 2000 rpm = IAC goes to zero (as above), then without letting go of throttle rev to above 2400rpm = this resets the IAC back to a reasonable level around 144 which leads to a normal idle.
I havent yet set the throttle blade to a greater value, Im sure it would reduce the impact of this problem, but seems to me I would be sweeping it under the rug, and there would still be some momentary low idle remaining as a result.

[HoldenTuner]

Im starting to wonder if this is a bug and every car with this ECU has the same issue, its just less noticeable since they have a stock camshaft....

[kevin87turbot]

The biggest problem that I see is that the IAC position is way too high at a warm idle. I typically target around 50 counts on the IAC once the engine is up to operating temp. Yours is around 100 counts. I'd adjust that first. Just open the throttle blade a little at a time until you get it there.

Next thing to adjust is your Base Running Airflow table. It's still too low. You are targeting 888 rpm idle speed at operating temp. Typically, you'd have a Base Airflow of at least 10-11 g/s on a 5.7L when you're targeting that high an idle speed. Your BRAF at operating temp is at 7 g/s now. You'll want to increase that substantially.

[Jay@HAP]

Is this a engine swap vehicle?

[Frost]

Your Throttle Follower Airflow Modifier table under 2400 RPMs is all zero. This has very likely caused the issue. For a test, but put that table back to stock. The STIT's should lock at a "remembered value" but they should NOT UPDATE like they are, when you are ON THROTTLE. It's trying to trim RPMs and return to idle while you are clearly on the pedal. Stopping the operation of the airflow adders and modifiers often has side effects like this. Like I said, put all of the Throttle Follower tables back to stock for just a minute and re-test.

[HoldenTuner]

Your Throttle Follower Airflow Modifier table under 2400 RPMs is all zero. This has very likely caused the issue. For a test, but put that table back to stock.

Frost thank you for your suggestion.
1st thing to mention is this table IS completely stock for a 2003 Australian Holden Commodore SS 5.7 LS1, I have compared it to my original saved table and 2 other Holdens from the repository (2x manual and 1x auto), all had the 2400rpm and below zeroed in the stock ECU..!!?

Why and how this can be stock I dont know, and I also cant tell you if it shows this issue on a bone stock car since I never drove with this engine stock,
and yes Jay@HAP its a Silvia engine conversion, but cant see how this changes anything unless BCM and MAFless delete somehow interacts with this?
Looking at the Chev Corvette 2003 LS1 hpt files in the repository I see they all have a different idea of stock for the 12112 Throttle Follower Airflow Mult table despite it being the exact same ECU and motor.

So, I changed it to the Corvette version of the table and problem solved..!!
Thanks again Frost for taking a proper look at the files and you clearly have a greater depth of knowledge than many, especially me.

Throttle Follower new.png

[Frost]

That's strange that it's like that OEM, but I've never tuned anything that was explicitly an older Commodore, so I had no file to compare. The name throttle-follower is a bit of a misnomer, as it is activated on application of throttle, but decays following the close of the blade. Once this airflow value has completely decayed, the STIT's resume operation for idle control if the vehicle is stationary. If the follower is never allowed to begin, many OS's will continue to trim airflow like this. We don't get to see control code, just variables, so we have to study to infer operation. It would seem that the OEM cars would have this issue as well if held at 2-2200 RPMS. Glad it's resolved!

[anniversaryss]

Frost thank you for your suggestion.
1st thing to mention is this table IS completely stock for a 2003 Australian Holden Commodore SS 5.7 LS1, I have compared it to my original saved table and 2 other Holdens from the repository (2x manual and 1x auto), all had the 2400rpm and below zeroed in the stock ECU..!!?

Why and how this can be stock I dont know, and I also cant tell you if it shows this issue on a bone stock car since I never drove with this engine stock,
and yes Jay@HAP its a Silvia engine conversion, but cant see how this changes anything unless BCM and MAFless delete somehow interacts with this?
Looking at the Chev Corvette 2003 LS1 hpt files in the repository I see they all have a different idea of stock for the 12112 Throttle Follower Airflow Mult table despite it being the exact same ECU and motor.

So, I changed it to the Corvette version of the table and problem solved..!!
Thanks again Frost for taking a proper look at the files and you clearly have a greater depth of knowledge than many, especially me.

Throttle Follower new.png

Well looks like i was mostly right. I did say i felt it had somthing to do with that. Sorry i haven't been around ive been real busy. I did check up on this a few times but figured i knew the others guys and their wealth of knowledge could help you better.

[Jay@HAP]

The reason I ask if it's a swap vehicle is because I've had a few swapped cars, were the PNDR needed to be changed because the PCM didn't know what gear it was in and caused all sorts of idle problems.

[HoldenTuner]

The reason I ask if it's a swap vehicle is because I've had a few swapped cars, were the PNDR needed to be changed because the PCM didn't know what gear it was in and caused all sorts of idle problems.

Ok, does the setting in hpt for Transmission/General/TransType Ive set to manual and PRNDL set to none and consider the ECU as always thinking its in PN cover that or theres more to it? because this engine and ECU was an auto and converted to manual.

Thanks to all who contributed suggestions in this thread.