5.3 Turbo Spark and Closed Loop issue

[Dynomite]

Hi Everyone,

Having a couple of issues with my tune on a 1954 Chevy 3100 with a Gen 3 5.3 with single GT45 98mm turbo. Currently set for around 8-10psi of boost.

First issue, any time I get into boost the spark tanks to -10 degrees, which is lowest value it will allow. I can't for the life of me figure out what table is causing it to go that low. I am logging KR and for most instances not seeing any knock. There are instances where I do see slight knock, which i'm assuming means i'm logging the right parameter. The base correction tables are fairly conservative as well. The IAT correction table would pull a couple of degrees, but not 20.

Second issue, I have closed loop and LTFT enabled, but it will not go in to closed loop. Is there a parameter i'm missing that's holding me out?

I appreciate anyone that has a look at my tune and log. Thanks,

Kevin
1954 Chevy 3100 5-3LS Turbo 4L80.hpt
part throttle drive 2.hpl

[blindsquirrel]

1954 Chevy 3100 5-3LS Turbo 4L80 - try this.hpt

No closed loop because both your O2 sensors are flatlined at the bias voltage. They're either not plugged in, or wired wrong, or dead/broken.

[Dynomite]

1954 Chevy 3100 5-3LS Turbo 4L80 - try this.hpt

No closed loop because both your O2 sensors are flatlined at the bias voltage. They're either not plugged in, or wired wrong, or dead/broken.

I suspected it was the sensors, so about an hour ago I replaced both of them. Took it for another drive, and actually got them reading and in Closed Loop for about 5 minutes, but then second half of my drive it was right back to open loop. Sorry, I forgot to save the log . Does that sound like a grounding issue then?

Kevin

[blindsquirrel]

It sounds like it could be anything that causes an open circuit on both sensor signal wires. Only you can narrow it down from there, when I look in GM service manuals there's no diagrams for a '54 3100 pickup (meaning, nobody else can know how it was wired in a swap like that other than the person who did it).

[blindsquirrel]

screenshot.12-05-2024 13.56.57.png

[Dynomite]

when I look in GM service manuals there's no diagrams for a '54 3100 pickup (meaning, nobody else can know how it was wired in a swap like that other than the person who did it).

Granted. Just wondered if an intermittent signal pointed in one direction more than another. Thanks.

Kevin.

[blindsquirrel]

Since you just replaced the sensors I assume you've already worked out whether the harness is set up for case ground or isolated and made sure the new sensors match the harness?

[Dynomite]

Since you just replaced the sensors I assume you've already worked out whether the harness is set up for case ground or isolated and made sure the new sensors match the harness?

I had no idea about the difference. On the scanner, my pcm is listed as a 2002 GMC Sierra. The sensors we matched up had them listed for a 2009 GMC Sierra. Could very well be the two different types not playing nice with one another here.

[blindsquirrel]

https://forum.hptuners.com/showthrea...ted-ground-O2s

[Dynomite]

https://forum.hptuners.com/showthrea...ted-ground-O2s

Yep, I read that thread a bit earlier. Definitely explains it well and i'm sure that's my issue. Now I just hope someone can have a look at my spark retard issue to see what's going on there.

[blindsquirrel]

Well... did you look at the changes I put in your file? Tried it yet? --> https://forum.hptuners.com/showthrea...l=1#post780297

[Dynomite]

Well... did you look at the changes I put in your file? Tried it yet? --> https://forum.hptuners.com/showthrea...l=1#post780297

Sorry I didn't notice it. I won't get to try it until tomorrow afternoon, I appreciate your help. The MAP calculated max is definitely one I missed as well as the burst knock. Thanks again!

Kevin

[Alvin]

Try this..

To me looks all TM related.


Also, I'd expect for 140 F IAT's with that much boost.. That will put the timing back to 0 with the way your main spark/Iat tables are setup.

1954 Chevy 3100 5-3LS Turbo 4L80. Alvin.hpt

[Dynomite]

Thanks to blindsquirrel and Alvin. You both spotted the problem with Torque Management. She pulls like a freight train now! Thanks again.

Kevin

[blindsquirrel]

All I did was turn off burst knock and the KS DTCs, and somebody'd been messin' where they shouldn't in the catalyst lightoff spark table...