GMPP Crate harness and E67 for LS3 has high idle and won't come down

[RMS-Man]

***I added the stock GMPP file and the file with idle set lower, but it still stays at 975rpm.***

IN READ GMPP.hpt

IN READ GMPP IDLE SET LOWER 1.hpt

Even when tune is changed to a lower commanded idle rpm.
Also when using the Scanner and the bi-directional controls the idle won't go below the preset 950 rpm that the GMPP tune came with.

Has anyone dealt with this before?

I've set all the idle minimums to 650 and commanded idle to 750 and even lowered the RAF idle tables down real low.

This is the 2nd GMPP crate harness and PCM I've had do this. It sux that we can't idle down to hear the nice cam lope at idle.

[LSxpwrdZ]

Yes same here... lowest I could get it to go was ~900rpm IIRC. I was forced to use Beta 2.25 at the time due to 2.24 not supporting them for some reason and thought it was just a bug in the Beta. Not had enough time to fart or report to HPT.

[RMS-Man]

The 1st car that did this I was using BETA and thought that was the issue.
This is the 2nd car that's done it and I'm using the latest Non-BETA and it still won't go any lower.

[DSteck]

Every GMPP one I've done has been screwed up. I tend to stay away from them.

[Luweegy]

Every GMPP one I've done has been screwed up. I tend to stay away from them.

DSTECK,
This is my tune.I've got a surge @ 2k rpm's and after i come to a stop the idle will creep up to 1400 rpm's? NW 102 TB,Lsxr 102 intake.Cam Specs are,SDPC Super stick 4,248/262,113 lobe center,685/648,Jessel rockers 1.9/1.85. I could use some help. Thanx, Tom

[edcmat-l1]

DSTECK,
This is my tune.I've got a surge @ 2k rpm's and after i come to a stop the idle will creep up to 1400 rpm's? NW 102 TB,Lsxr 102 intake.Cam Specs are,SDPC Super stick 4,248/262,113 lobe center,685/648,Jessel rockers 1.9/1.85. I could use some help. Thanx, Tom

Your calibration is not a GMPP cal. So, kind of not in the same discussion.

As for your idle creeping up when you stop, you've got a bazillion grams of idle airflow. Even for a 102, with the scalar set to 7200. Your tune needs a lot of idle work.

[edcmat-l1]

Every GMPP one I've done has been screwed up. I tend to stay away from them.

I haven't done one in a while, but I've done a bunch of them. I've got a data log of one idling at 775ish. But like I said it's been a while since I've tuned one.

[Luweegy]

edcmat-l1 Is this something you could retune for me? I realize this isn't a GMPP tune.Should I move this post some where else?

[daniel76309]

I have LS376-480 with the GMPP controller package, and I have the same situation. No matter what I have tried, it won't idle less than about 850. I can go higher, but no lower. It isn't a horrible thing, but it would be nice to be able to control it. If someone figures it out, please share.

[ElecTech]

Even when tune is changed to a lower commanded idle rpm.
Also when using the Scanner and the bi-directional controls the idle won't go below the preset 950 rpm that the GMPP tune came with.

Has anyone dealt with this before? I don't have the file to post until this evening.

I've set all the idle minimums to 650 and commanded idle to 750 and even lowered the RAF idle tables down real low.

This is the 2nd GMPP crate harness and PCM I've had do this. It sux that we can't idle down to hear the nice cam lope at idle.

What release is the file you're using? Some of the earlier ones were real bad, but the newer stuff is much better. The one I just did idled at 875.

Can you post a file?

[doc350]

I just fired up a Chevelle with a LS3 using the GMPP harness and didn't notice and odd idle characteristics. I didn't have it running for long though. I will look into it more on Monday and post some logs and the file if anyone is interested in seeing them.

[RMS-Man]

***I added the stock GMPP file and the file with idle set lower, but it still stays at 975rpm.***

IN READ GMPP.hpt

IN READ GMPP IDLE SET LOWER 1.hpt

[RMS-Man]

idle to high.jpg

This is the idle even with the changes to lower it. Even the TPS stays high at 20%

[gmtech16450yz]

idle to high.jpg

This is the idle even with the changes to lower it. Even the TPS stays high at 20%

I looked at your idle settings and those first ones before you lowered things looked WAY off! The airflow stuff doesn't look that bad after you tried to lower it, but there are some other differences that may be causing your high idle. You don't have much idle spark control, that will help lower your idle speed. Not exactly how I'd want to do it since your idle timing looked decent already. Giving it more idle timing control will retard it more, which will definitely lower the idle, but it will also make it lose a little efficiency. You might actually like that if you want to give it a big cam idle!

Try making these changes in my screen shot here. They don't have to be exact obviously but you'll get the idea. Also, lower your "Idle Airflow Multiplier vs. ECT". Try starting with a 10% reduction across the whole table. Yours might be a little high adding to the airflow changes you made in the other tables. (I actually should have told you this FIRST. I'd try this before doing anything else. The 20% throttle is obviously telling you that there's too much airflow.

BTW there's a ton of PID's you should also be looking at that aren't in your table. One in particular that helps identify idle issues is "Idle Adapt Advance". That one will show you if the ECM is trying to control idle by either advancing or retarding the base timing. If it's at zero and your idle is super high, that could mean the ECM "thinks" that the desired and actual idle speeds are ok. If it's super retarded, that means you have too much airflow and obviously if it's way advanced it means you need more airflow. You want enough idle ign timing so that it runs efficiently, but not so high that the ECM can't advance it further to control low idle speeds. It's all a balancing act between airflow and ign timing.

Hope that helps and I hope it wasn't obvious stuff you already knew! Sorry if it was. Good luck!

Edit- BTW why are your 02 sensors stuck full rich?

[Ray]

I'd lower your Final Idle Airflow Minimums way down - that seemed to help me.

My 5.3 w/ manual trans GMPP Crate Controller/harness idles at 750 (or what ever speed I set) great.

Capture.JPG

[[email protected]]

ray, can you post that file.
i have what says in the vin LS376_rev4, which i interpret to be revision 4 of the software and it has spark adjust tables like gmtech is saying to change to (btw, i have older file and those tables are junk - they aren't even complete and +/- 7 degrees and idle airflow table are all over the place, almost as if the file is corrupt). so this is much better file, but it still won't go lower than 875.
as well, the idle minimums are too low and same for startup (at least this engine).
i'm sure i can idle at 750, would like to get it there.

[Jabbott]

Have you tried to just to a tis flash to something else? I just finished my race with the e67 gmpp but I had the idle setup high. never tried to go below 900 so I dont know if it was an issue or not. My car had a huge came and a 5lb clutch so the idle was set high to help with that.