Helping a friend on his 70 c10 L83 swap. It has a BTR stage 2 truck cam with 4 deg limiter. Using a PSI wire harness. Engine, ecu, and peddle out of a 2015 Tahoe.
The biggest issue is getting the idle RPM to my commanded RPM. No matter what i adjust it stays around 1100 rpm or so. what am I missing?
attaching log and tune.
One thing I see is the peddle TQ at idle is -41 and stays there with every tune.
Thanks for any help
Last edited by Speed39; 2 Weeks Ago at 04:08 PM.
Last time and the only time I've ever had one do this, it was due to cat lightoff. Due to the 10% lean on the wideband and the - torque at idle, I'm assuming you don't have rear o2's???
Then check the usuals like making sure you don't have the stupid valve cover breathers causing a vacuum leak or anything like that, but usually when you get hung at 1200 it's stuck trying to do something.
Last edited by GHuggins; 2 Weeks Ago at 10:38 PM.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Copy that and yes no rear o2's. He has those Valve cover breathers going into a filter to atmosphere. One thing I didn't try because of a brain fart is rescale the throttle body size. I am assuming making the ecu think it has a larger TB will close the throttle blade? I had the VVE and VTQ all over the place with the same results. It does idle fairly well at that rpm but of course isn't right. I wanted him to put route the valve cover breathers into the intake tube but he hasn't yet.Originally Posted by GHuggins
I also didn't know why the external load was 0ed out? Not sure what affect that would have? I would say fix the vacuum leak caused by the breathers, install the o2s then fix the external load and go from there.
It has a bunch of codes including ambient air temp and brake pedal position and the brake pedal code is current. Wonder if that's causing any additional airflow like an off idle adder, throttle follower, etc. Surprised the timing isn't working any harder to pull it down.
Not a very good pid list to try and diag. the problem.
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External load is per oil temp. This harness must not have provision for the oil temp. It always reads -40. I tried all sorts of setting on that table with zero change, so last tune yesterday I zeroed it out to see what it would do and no change. So, you say cap those vents or run them to the intake tube?
He is a couple hours from me so that's an issue but going back tomorrow and take another stab at it. It has front o2's, no cats.
Thanks for the help20240320_172122.jpg
I agree with ya on the PID list. I will add to that on Friday. This PSI swop harness doesn't have Ambient air temp and Brake pedal position, that I am aware of. This was all installed before I was involved.
One of your torque source pids should tell you if it's in idle mode or not. That will tell you if it's related to the missing brake pedal input.
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Yes like Ed said and get rid of the breathers. If you think about it. You have breathers to allow in unmetered air and vacuum being pulled on the valley bypassing the TB that's not helping things. However, when it hangs at 1200 without self revving higher, its almost always hung up on cat related test. Sounds like a poor designed harness if it doesn't have any provisions for anything.
Copy that. Thanks
I got ya on that. I am thinking the harness leaves a lot to be desired. He had bought the engine, trans, peddle and harness from a guy that decided not to move forward with his swop. Hard to get info from PSI since he wasn't the original purchaser. I am close and being my first GM tune experience, its a tad different than Dodge which I have done .
I do appreciate the pointers and help.
DTC log details.jpg
Codes....
As for the harness I think everyone is still making them like we're still on GEN3 PCMs and they don't have a lot of stuff that's needed on the later GEN4 and now GEN5 stuff.
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Swaptime makes the best harnesses. Mitch has gone to putting the correct connectors for the different years along with including things such as supply pressure sensors, fpcm's if wanted, the correct injector harnesses for OS breakpoints and so on. I would say his kits are the best out there. Some of his older stuff was missing some things here and there, but you could work around it. His newest stuff has just about everything to my knowledge to keep it as OE as possible.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
I'll bookmark that page. I have not dealt with them before.
EFI specialist
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Hmmm. Yea I see now. I don't get that much info. Maybe i have the scanner set up wrong. I will look into that.
Thanks
Ive heard of them. When I Decide to LT swap my 64 Riviera I will not use PSI. Swaptime will be what I use.
Last edited by Speed39; 2 Weeks Ago at 04:07 PM.
FYI, swap is spelled with an A.
EFI specialist
Advanced diagnostics, tuning, emissions
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email=[email protected]
My bad!
Went back to try some more on the c10. I did make some progress, but it's still not close. I was however able to get it to idle somewhat better
but fueling is not good. I know the tune is all wacked out and I'm not logging or have the histogram setup properly.
I need to get him to bring me the truck so I don't have to waste 4 hrs. each time I go to give it a try.
I am 100% new to any GM tuning and starting with a Gen 5 makes it worse I would think. Any help is greatly appreciated.
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