2006 GTO 6.0 LS2 6spd Manual H/C/I with surging idle at cold start

[somturboss]

This is my brother's car and he had it tuned after all the mods (heads, cam and intake but I don't know the specifics) were done but the idle was never quite right. He made a change to his throttle body and now it surges during a cold start up. I've tried a few tips from the posts on here and I was able to get the idle to smooth out but then the rpms start climbing and it sits at 2,000 rpm even after I changed everything to 800 rpm. I returned the tune to the as found from the tuner and I will post it along with the scan. I'm not sure if the scan has all the necessary info so I apologize in advance.


GTO scan with as found tune surging.hplGTO AS FOUND TUNE FROM MADD TUNING.hpt

[ns158sl]

He made a change to his throttle body and now it surges during a cold start up.

GTO scan with as found tune surging.hplGTO AS FOUND TUNE FROM MADD TUNING.hpt

What did he change?

[blindsquirrel]

Trouble Codes:
P2176 - Throttle Actuator Control System - Idle Position Not Learned (Pending, Current)

[ns158sl]

Thats not it. It is in the TOON lol

[blindsquirrel]

Just needs that code turned off, right? Like the old days of a piece of black tape over the check engine light.

[somturboss]

There are no engine codes or check engine lights but on the center info display it says safety mode/reduced performance.

[edcmat-l1]

Just needs that code turned off, right? Like the old days of a piece of black tape over the check engine light.

That's so ghetto. Take the dang bulb out for goodness sakes LOL

[edcmat-l1]

Yeah I'd be pretty MADD if I paid for that.

[blindsquirrel]

There are no engine codes or check engine lights but on the center info display it says safety mode/reduced performance.

The log file you posted disagrees with that statement.

screenshot.11-08-2024 07.24.06.png

[somturboss]

Thank you! I never saw that and assumed a check engine light on the dash would illuminate. I'm very new to all of this.

[somturboss]

It was the factory 90mm throttle ported to match the fast 92 intake but too much was removed and with the throttle blade closed it had too much air leaking around the throttle blade. The tuner tried compensating for this but the lowest he could get the idle was 1000 rpm (I'm not sure what changes he made). The throttle body was reworked to tighten the clearances around the blade and that's when the surging began. I'm still researching how to relearn the throttle body but I would suspect I'll need to make some tuning changes to the idle if the reworked throttle body fixed the airflow issue.

[somturboss]

The log file you posted disagrees with that statement.

screenshot.11-08-2024 07.24.06.png

I Tried the throttle body cleaned tab in the hp tuners scanner, turning the ignition on for 3 minutes off 1 minute on 3 minutes and off 1 minute, and the battery was disconnected last night. I also verified that the wiring is plugged into the throttle body. It still surges at idle and won't let me go over 15mph.
Am I missing something on the relearn process?

This is the latest log where I let it idle for 3 minutes and went for a drive.

GTO scan after throttle clean in hptuners.hpl

[SiriusC1024]

Buy a new factory tb and don't port it this time. If you watch MAP during WOT it'll tell you if you need a bigger tb or not. Likely not.

[somturboss]

Buy a new factory tb and don't port it this time. If you watch MAP during WOT it'll tell you if you need a bigger tb or not. Likely not.

Thanks for the suggestion. I passed this info onto him and later today he tells me he ordered a Speed Master 92mm from Jegs instead of a factory one. Hopefully it's not junk.

[blindsquirrel]

Some people enjoy punching themselves in the face over and over, not much you can do to help them when they don't want it.

[Alvin]

Thanks for the suggestion. I passed this info onto him and later today he tells me he ordered a Speed Master 92mm from Jegs instead of a factory one. Hopefully it's not junk.

there are practically 0 gains from any throttle body or porting on even the most radical NA setups. I'd go back to a factory throttle body.

[somturboss]

there are practically 0 gains from any throttle body or porting on even the most radical NA setups. I'd go back to a factory throttle body.

Thank you, I appreciate the advice! He is looking into a factory replacement now. Just out of curiosity, was I doing the throttle body relearn procedure correctly?

I cleared the codes, tried the throttle body cleaned tab in the hp tuners scanner, turning the ignition on for 3 minutes off 1 minute on 3 minutes and off 1 minute, then let it idle for 3 minutes. and went for a short drive. It still surges at idle and won't let me go over 15mph because it's in the safety mode/ reduced performance. And the throttle body says it still needs to relearn.
Am I missing something on the relearn process?

[Alvin]

i've never needed to do a throttle body relearn for anything.... well some gen 5 stuff but that is a different story. There is a "throttle cleaned" button in the scanner you can try.

[somturboss]

i've never needed to do a throttle body relearn for anything.... well some gen 5 stuff but that is a different story. There is a "throttle cleaned" button in the scanner you can try.

Good to know! I guess that's more evidence that the throttle body is the culprit.

[somturboss]

Just wanted to update this thread with my results just in case it may help someone else in the future. After some research I read that the LS2 throttle body is known to have issues, so we went with a new AC Delco LS3 instead because it was improved upon and supposed to be an upgrade. After installation, the aggressive surge at idle was gone and it idled fairly smooth at 1000 RPM with no attempts to relearn the throttle body. I added air and smoothed out the Idle Air Flow minimum table, added 13 degrees of timing to the Idle spark advance in the 1200rpm and below to .44 g/s range and dropped the rpm to 850 rpm and it idles perfect. I'll continue to tune these settings but it's a huge improvement.

I learned a lot while troubleshooting this and I appreciate the replies that pointed me in the right direction. Definitely a newbie mistake not looking at the DTC's but now I know!