Gen 3 5.3 LS Leaning out

Good Morning,

First, I'll start by saying I'm a long time lurker, first time poster. Also, I am NOT a professional when it comes to tuning however I've been able to learn enough to be dangerous. I built my LS from the ground up. New bottom end, new top end, cammed, ported heads, TBSS intake, Injectors, the works....

I've been able to get it to run and drive pretty damn good but when you start stepping on it, and letting her eat, she will erroneously lean out and won't come out of it until you shut her down, let it sit for a minute, and then start it back up. It will then run like it's cold as hell (even though my ECT's are well above 170) and then when the LTFT's kick it, she will run like a champ again and away I go. Oh, and it also throws me random misfires. I know about the misfire count but I don't understand specifically what that means so if someone could direct me on that, that would be much appreciated.

Included, I have the tune that she is currently on (as of 9 November 2024 0934) and the log that I just took. If you watch the log, you will see where I really get into it, and then looking at the AFR, you'll see it will peg out at 18+. Can someone please help me figure this out? This issue is getting really annoying.

One last thing, my VCM Scanner will occasionally quit logging as well! What's that all about?? Makes it really hard to get a good long log if it will automatically quit logging, or quit registering values. Is that a connection issue? Software issue? Computer issue? What am I dealing with here?

Of course it's going to run like dogshit if it's trying to run in closed loop while both O2 signals are shorted to ground. Look at the O2 mV's, they never move from 4 (four!) mV for the entire log.

And after you fix whatever's causing that, you'll have to look into why it 'runs good' but only when the LT+ST are adding a combined 80%.

Quote:

---

Originally Posted by blindsquirrel

Of course it's going to run like dogshit if it's trying to run in closed loop while both O2 signals are shorted to ground. Look at the O2 mV's, they never move from 4 (four!) mV for the entire log.

---

I knew they weren't working, I did check the fuse that supplies them the voltage and it's not blown. I also checked to make sure they were connected and they were but I know that doesn't really mean much in the grand scheme of things. I'll investigate further when I have more time.

Engine swapped vehicle or no?
What is the fuel system?
What fuel pressure regulator?
What injector part number?

Injector data is incomplete, the Offset table is still stock 2001 LQ4 (which was referenced/return style). The flow rate table is flat as if for a referenced/return style.

Quote:

---

Originally Posted by MtnPwnd

I knew they weren't working, I did check the fuse that supplies them the voltage and it's not blown. I also checked to make sure they were connected and they were but I know that doesn't really mean much in the grand scheme of things. I'll investigate further when I have more time.

---

The fuse is for the heaters. The signal lines have what is called a 'bias voltage', which means at either Stoich or open circuit, the O2s should display that bias voltage of 450mV. Less than 450 is either lean or short to ground. Above 450 is either rich or short to voltage. The only real way the signal can be flatlined either high or low is if the signal circuits are shorted to ground/power somewhere.

Do you have an isolated ground harness with isolated ground sensors, or case ground harness with case ground sensors? Or is it a mix-n-match?

Quote:

---

Originally Posted by blindsquirrel

Engine swapped vehicle or no?
What is the fuel system?
What fuel pressure regulator?
What injector part number?

Injector data is incomplete, the Offset table is still stock 2001 LQ4 (which was referenced/return style). The flow rate table is flat as if for a referenced/return style.

---

Engine Swapped Vehicle or no : Yes, 5.3 Iron block from a 2000 silverado swapped into a 2000 GMC Sonoma
Fuel System : Return Less style deadheaded system. FPR set to 58psi not vaccum referenced
Injector part number : Idk the part number. All I can tell you is they are stock TBSS injectors

TBSS only ever came with 29lb 19421333/12580681 injectors. But if by 'TBSS' you just mean 'the bigger boxy Gen 4 truck cathedral port intake' then it could be several different injector part numbers.

What is the specific fuel pressure regulator please. Part number. Name. Link to product page, something.

Quote:

---

Originally Posted by blindsquirrel

TBSS only ever came with 29lb 19421333/12580681 injectors. But if by 'TBSS' you just mean 'the bigger boxy Gen 4 truck cathedral port intake' then it could be several different injector part numbers.

What is the specific fuel pressure regulator please. Part number. Name. Link to product page, something.

---

I'm going to pm you. I do appreciate you replying.

No you are not going to fucking PM me. This is a public forum, the point of which is your questions and the answers you get help other people who may not be reading this until years from now.

Wow, ok no need to be like that. But fair enough, I'll reply later with the details you were looking for later.

Im surprised it drives lol. Your MAF and VE need a lot of work, like a lot. If at a minimum try to get the p/n off the injector that is physically in the car. Might need to change oil if you keep running it like that with all the fuel in the oil.

No need to be like what? What part of this discussion needs to be private?

Quote:

---

Originally Posted by ns158sl

Im surprised it drives lol. Your MAF and VE need a lot of work, like a lot. If at a minimum try to get the p/n off the injector that is physically in the car. Might need to change oil if you keep running it like that with all the fuel in the oil.

---

Honestly that makes a lot of sense with how fast I run through gas, and the viscosity of the oil when I change it. Please remember, I am not a pro at this. This is my first vehicle I've ever done this with.

It's so rich because the O2s are stuck full lean, and the trims are adding fuel and adding fuel and adding fuel trying to get the O2 volts up off the floor, and it can't, because the O2s are not measuring what is in the exhaust they are measuring battery ground.

Quote:

---

Originally Posted by blindsquirrel

It's so rich because the O2s are stuck full lean, and the trims are adding fuel and adding fuel and adding fuel trying to get the O2 volts up off the floor, and it can't, because the O2s are not measuring what is in the exhaust they are measuring battery ground.

---

That makes sense too. I'll troubleshoot that when I get home today to see where the issue is.

Blind, in regards to your question earlier about the fuel pressure regulator. It's a fuel lab 51506. See link below.

https://fuelab.com/custom-fuel-press...ets-51506/p385

What you're getting is a result of the O2 problems, plus the injector data (if you didn't know the part number, where did the numbers in the flow rate table come from?), plus the unrealistic VE/MAF. Just so you don't go assuming that fixing any one single thing is going to show positive results.

Quote:

---

Originally Posted by blindsquirrel

What you're getting is a result of the O2 problems, plus the injector data (if you didn't know the part number, where did the numbers in the flow rate table come from?), plus the unrealistic VE/MAF. Just so you don't go assuming that fixing any one single thing is going to show positive results.

---

Before you read on, please be advised and remember, not a problem. Haven't ever done this before, and just trying to get their rig going. I don't know anything about any of this so this is all new to me.


The injector data that is in there is a combination of me Google searching, "Typical tbss injector size" and watching GREG'S video about injector scaling, and paying attention to Matt Sanford's method of running a returnless style fuel system.

And yes, I completely understand that fixing just the o2's isn't going to rectify the problem completely, but it's definitely going to help the situation.

Dammit, that was supposed to say, "Not a PRO." Not problem.

Jesus, and it says "their" implying that I'm doing this for someone else....I'm not. It's for my truck...

See the link down below this post? It's a spreadsheet where I converted all the good Gen 4 injectors over to Gen 3 format. Whatever yours turn out to be after verifying the number, will be in there. Flow rate is the least important of all the injector data.

Quote:

---

Originally Posted by blindsquirrel

See the link down below this post? It's a spreadsheet where I converted all the good Gen 4 injectors over to Gen 3 format. Whatever yours turn out to be after verifying the number, will be in there. Flow rate is the least important of all the injector data.

---

Good to know, thanks man. I'll look into it.

Again, dont waste your time tooning until you can get the O2s sorted.

And please don't be driving it around like this. You're still at the 'put together a base file correct for all the hardware being used' stage.

Quote:

---

Originally Posted by MtnPwnd

Before you read on, please be advised and remember, not a problem. Haven't ever done this before, and just trying to get their rig going. I don't know anything about any of this so this is all new to me.


The injector data that is in there is a combination of me Google searching, "Typical tbss injector size" and watching GREG'S video about injector scaling, and paying attention to Matt Sanford's method of running a returnless style fuel system.

And yes, I completely understand that fixing just the o2's isn't going to rectify the problem completely, but it's definitely going to help the situation.

---

The injectors have a part number on them... Just post it here.

Quick update about the o2 Sensors.

B1S1 Sensor works as intended but only if B1S2 is unplugged. As soon as it's plugged in, it sends them both shorted. So I tested between the pins and B1S2 connector is shorted between the ground and the H2OS Low side. However, it's not in the harness because I unplugged the Blue C1 connector from the PCM to test continuity to ground and it wasn't there. Then I went back to the connector and retested there, no short to be found. It only appears when I plug it into the PCM, so I thought, "Ok, PCMs aren't perfect, sometimes they go bad (though very rarely)" so I programmed another PCM, and same issue so it's got to be something else. I'll look more into it tomorrow when the sun comes back.

Case ground harness or isolated ground harness? And case ground sensors or isolated ground sensors? And is the harness the same type as the sensors? By the way, what is the harness - factory, good aftermarket, crap Chinese aftermarket?

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

Quote:

---

Originally Posted by blindsquirrel

Case ground harness or isolated ground harness? And case ground sensors or isolated ground sensors? And is the harness the same type as the sensors? By the way, what is the harness - factory, good aftermarket, crap Chinese aftermarket?

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

---

Good Morning Blind, thanks for shooting that link. That helps a lot and explains why I'm seeing the continuity between the ground and Pin A (when C1 is connected to the PCM) so it's a case ground harness. I'll check the o2 sensor by unthreading it from the exhaust and completely isolated for the set up there.

Additionally, I found that I have the 29lb injectors pn# 12580681. Your spreadsheet was instrumental in fixing that mistake so I thank you for that.

Just downloaded the injector data into the truck and ALREADY made a HUGE difference. It doesn't chug at first until it "warms up" and adds 80% fueling....Blind, thank you so much for that spreadsheet.