High Throttle at Idle

[SJ90]

I've been fighting my idle for months now. It seems to be software since I can see the car commanding what it is doing, it's just what it is commanding isn't what the tune should be asking for.

I've attached my tune and a log, but something has changed, and the ECU is now commanding a higher throttle without changing the tune. I can load old tunes that I have logs showing they used to command ~18% TPS at idle, and are now commanding ~21%. Both of those are high, and they should be commanding ~16%, but no matter what I change it won't go that low until adaptive idle kicks in.

So for now, any tips on why the exact same tune would be commanding 3% more throttle at idle?

The only thing that changed is I flashed the fuel pump control module with my tech II copy. But I don't know if that would have any effect

[Lakegoat]

Did you install a larger throttle body. ETC Scalar shows 8191.----. I just looked at a stock 2013 and it was 5060.----

[SJ90]

Nope, stock TB. With the stock area, it calls for even more, like 23% I believe.

[blindsquirrel]

There's a thing in the scanner special functions for 'cleaned throttle'. TPS % too high regardless of BRAF and negative timing are pretty clear signs. Key on, special functions, click button, wait... some unspecified number of seconds (15-20), key off, wait another number of seconds, start engine. Tech2 is better at this, it gives feedback for if it's completed or not and tells you what to do and when.

[blindsquirrel]

Looking at the 1st logfile... after your drive, it seems to have come back to reality (16% TPS, normal idle spark numbers). But the first period of idle before the drive it's clearly trying to bring the idle speed down with timing, and doesn't want to (or doesn't think it's allowed to) close the throttle to less than 21-22%.

[SJ90]

There's a thing in the scanner special functions for 'cleaned throttle'. TPS % too high regardless of BRAF and negative timing are pretty clear signs. Key on, special functions, click button, wait... some unspecified number of seconds (15-20), key off, wait another number of seconds, start engine. Tech2 is better at this, it gives feedback for if it's completed or not and tells you what to do and when.

Okay cool, I'll give this a try and let you know if I get anywhere. Thanks!

Looking at the 1st logfile... after your drive, it seems to have come back to reality (16% TPS, normal idle spark numbers). But the first period of idle before the drive it's clearly trying to bring the idle speed down with timing, and doesn't want to (or doesn't think it's allowed to) close the throttle to less than 21-22%.

It settles down to around 16% after a few seconds of idle. I have my idle min speed set to 50 KPH, so sometimes it is down to 16% by the time I stop, sometimes not. But if I blip the throttle, it goes back up to 21% for a few seconds, then starts pulling throttle back to 16%.

[smokeshow]

I think I'm missing the problem. You're describing behavior that is normal.

[SJ90]

No luck on the relearn. I did both a sweep and position relearn. It is still idling way high when returning to idle. Calling for the same 21% throttle.

I think I'm missing the problem. You're describing behavior that is normal.

Yeah, sounds like you missed what I was describing. It is idling at 1,000-1,200 RPM when returning to idle and stays there rock steady for at least 3 seconds, the target is 650. After about 3-5 seconds goes by, adaptive throttle kicks in and brings the RPM down to target.

[SJ90]

This is a zoomed-in view of the issue. You can see the throttle and RPM stay high for about 4 seconds before it starts pulling throttle.
High Idle.JPG

[SJ90]

Looks like this isn't an easy problem...

Little more info, the only way I've been able to avoid the high idle is by limiting the max idle throttle area. If I set it to around 0.35%, the throttle goes straight to 18.8, then slowly falls to 16ish the same as before. It still does the high hold, but at least this is manageable and holds around 850 rpm when hot. Down side is it makes of throttle abrupt and cold stays very difficult.

I'm getting close to giving up and buying a standalone. It seems crazy, but I can't live with a car that is a pain to drive as my daily.

[SJ90]

I found some interesting things out today, I logged basically everything that I could find that had throttle in it. What I found is that they do not read the same. I've attached the log, but here is the summary:

- Throttle Position (SAE) is what I have been logging this whole time and it still reads as before. We'll use this at 18.4%, all other readings are taken at this point.
- Absolute Throttle Position B (SAE) = 18.4%
- Throttle Position = 7.5%
- Throttle Position 2 = 2.7%
- Commanded Throttle Actuator (SAE) = 7.1%
- Throttle Desired Position = 7.1%
- Relative Throttle Position (SAE) = 5.1%
- Throttle Position = 4.08V
- Throttle Position 2 = 0.90V

Does anyone know what all these are actually recording?
Is it normal for them to be so different?

The other thing I noticed, while logging my Thottle Position (SAE) bounces around like crazy when logging all the above channels. If I remove the channels it is smooth again.
https://www.veed.io/view/4ffa4b1f-c1...ingWidget=true

[blindsquirrel]

Don't use the (SAE) channels for GM electronic throttle stuff.

[SJ90]

Don't use the (SAE) channels for GM electronic throttle stuff.

Okay, good to know. Any idea which of these throttle position channels to use?

I think it is important because #1 reads something close to what I see in other people's logs. #2 and #3 read way less. If #2 or #3 is the correct channel, then I think I've got a vacuum leak that I can't find for the life of me.

Notes:
- Desired throttle and #1 match almost exactly.
- #1 reads 0-100%
- #2/3 read 0-40%

Spencer

[SJ90]

Can anyone do me a solid and record these channels on an E38/E67 for me?

I would like to see if my TP 2 sensor is reading correctly. I'm hoping it is not and that is what is causing this issue....

[mbray01]

Put your idle timing back to stock
start there

[SJ90]

No luck with that either. It will idle about a 100 RPM lower due to the cut timing, but the throttle is still hanging open.

The part gets me is I can load exactly the same tune as last fall, and it will now hang when it didn't before. I've looked at the logs and once the adaptive throttle kicks in and brings the idle down, the TPS and TPS2 are the same now as then. So it doesn't seem to be hardware or tune. It's like there is something in the ECU that is not being written anymore that controls the commanded throttle when first going to idle.

I've tried returning to stock and writing the newest calibration from sps, but still no difference.

[smokeshow]

Looked at this again... There are a lot of questionable cals that you no doubt have ben tweaking to see what works...but some are doing more harm than good. One of those is setting all of the idle speed targets to exactly the value of the minimum RPM reference. You cannot command the minimum allowable idle speed because crossing that threshold disables throttle adaptive idle. You still have spark control, but the throttle idle control is frozen. Definitely start there and put the rest of your adaptive idle cals back to stock.

[GHuggins]

You might even want to do a "full write" as some of gm's ealier cals wouldn't allow you to reset throttle, perform a clean reset where it actually worked without doing a full write. It was something in the KAM that stored the last throttle idle settings that would cause them to high idle without any control. You either had to do a full write or drive for a couple of weeks hoping it would "self re-learn". I ran into this the most with trailblazers doing "actual" throttle cleans where you couldn't get them to idle below 2000 rpms in severe instances.... OS differences are what makes all of us tuner's look like idiots sometimes Especially when one doesn't do anything it's supposed to do.

[cadillactech]

You might even want to do a "full write" as some of gm's ealier cals wouldn't allow you to reset throttle, perform a clean reset where it actually worked without doing a full write. It was something in the KAM that stored the last throttle idle settings that would cause them to high idle without any control. You either had to do a full write or drive for a couple of weeks hoping it would "self re-learn". I ran into this the most with trailblazers doing "actual" throttle cleans where you couldn't get them to idle below 2000 rpms in severe instances.... OS differences are what makes all of us tuner's look like idiots sometimes Especially when one doesn't do anything it's supposed to do.

Exactly this. I had this happen many times to where you had to do a replace and program using SPS to get the idle to come back.

[SJ90]

Looked at this again... There are a lot of questionable cals that you no doubt have ben tweaking to see what works...but some are doing more harm than good. One of those is setting all of the idle speed targets to exactly the value of the minimum RPM reference. You cannot command the minimum allowable idle speed because crossing that threshold disables throttle adaptive idle. You still have spark control, but the throttle idle control is frozen. Definitely start there and put the rest of your adaptive idle cals back to stock.

Okay, I've tried it with all stock idle settings and all stock idle except the TB size and Min airflow. Here are the files. I used another site since the size limits here kill the logs.

Tunes here: https://ufile.io/f/fgpsh
Logs here: https://ufile.io/f/yxbua

The strange part is it idles super high coasting down to a stop, but once stopped it comes back to some kind of normal. Pushing the clutch in also brings it down.