About to take my car out back and shoot it. Lean/rich spikes and cannot figure it out

[lwrs10]

I keep having insane lean, then insane rich spikes in my truck. It happens open or closed loop, speed density or MAF tuned. It always happens under heavy load, but not full throttle. It really shows up when the torque converter locks up at 46mph.

It happens same load, same MAP KPA, same MAF HZ, same everything as other hits....in the hundreds....that were fine.

This is a custom everything engine. Vortec 350, custom intake, custom fuel system with LS3 injectors, fuel pressure is 58psi, all ran by an 0411 computer in my S10. Since we do not have a "bastard child" forum, I think it fits best here since it uses an 0411 setup.

Attached is my tune and log files. Also included my scanner config file if you want to see what i am logging.

The frames you want to look at is:

1611-1773
2475-2571
11090-11223

Please, for the love of god, help me out here. Before I set it on fire.

[STR8BALLN]

Looks like Bank 2 O2 is reading lean the majority of the time especially when cruising around 70mph. I would look into that. Either you are really lean or the O2 is bad. Its should be switching more than that. Are you using Bosch O2's?

I noticed your injector flow rate vs. KPA is 41.74 straight across vs worked with the numbers at different KPA from an updated 2008-09 LS3 vette or 2010-present Camaro.

Here is what I used for my LS3 injectors:
41.74 42.20 42.54 43.00 43.40 43.84 44.21 44.64 45.10 45.51 45.90 46.32 46.80 47.20 47.60 48.00 49.00

I also left my injector pulsewidth at 1.277

[lwrs10]

its in open loop, so the O2 sensor readings are not right. I am cruising right about 14.9 at 70, so it should show lean, and there will not be switching happening. The wideband is what needs to be looked at here.

my injector flow rate is correct....I have a return style fuel system. You set it flat across the board with a return system.

[lwrs10]

I hope someone can guide me towards what is wrong....

[jimmyblue]

One thing I recommend is logging with a minimum PID set.
It's my belief that there is a lot going on that's "too fast to
see" at the available frame-rate, and a precursor event
might be missed.

One such event could be a misfire, at least for a lean spike
at the sensor. What would precipitate one, I dunno specifically.

Now with the remark about TCC locking, I do wonder about
ground integrity and how sensors might be affected by
power spikes and ground spikes (load apply, load dump,
stuff running through chassis sheet metal vs the explicit
ground braids and so on). Ground quality dogs the wideband
setups a lot.

For that matter EMI is a concern on some sensors, the
GM manuals specifically mention it for MAF debug issues
and it's conceivable that O2 sensors with their fairly high
output impedance could pick up voltage noise too. You
could unbundle them and move them away from any
wires that have sparse duty high current signals or
full scale voltage switching activity, if you get desperate
for things to try.

[lwrs10]

One thing I recommend is logging with a minimum PID set.
It's my belief that there is a lot going on that's "too fast to
see" at the available frame-rate, and a precursor event
might be missed.

One such event could be a misfire, at least for a lean spike
at the sensor. What would precipitate one, I dunno specifically.

Now with the remark about TCC locking, I do wonder about
ground integrity and how sensors might be affected by
power spikes and ground spikes (load apply, load dump,
stuff running through chassis sheet metal vs the explicit
ground braids and so on). Ground quality dogs the wideband
setups a lot.

For that matter EMI is a concern on some sensors, the
GM manuals specifically mention it for MAF debug issues
and it's conceivable that O2 sensors with their fairly high
output impedance could pick up voltage noise too. You
could unbundle them and move them away from any
wires that have sparse duty high current signals or
full scale voltage switching activity, if you get desperate
for things to try.

i completely agree with you about minimal logging, but I am trying to log anything and everything I can think of that could remotely cause this issue in that scan.

[jimmyblue]

Sure, but you may need to do it in multiple logs of fewer
PIDs apiece, throw away PIDs that looked "inactive" and
collect ones that have something going on for another
run, etc.

The triangular character of the O2 sensor waveforms
at the "spike" says that you're up against sample rate,
or the signal is some spurious glitch, while other regions
of sensor reswitching (normal) activity are slower and
have curvature etc.

I'm not convinced the lean spikes are real, just looking
at the scan. Are they attended by anything the butt-o-
meter can sense (a cough, drivetrain jerk, ...)? Or are
you chasing a ghost that doesn't affect anything?

[lwrs10]

Sure, but you may need to do it in multiple logs of fewer
PIDs apiece, throw away PIDs that looked "inactive" and
collect ones that have something going on for another
run, etc.

The triangular character of the O2 sensor waveforms
at the "spike" says that you're up against sample rate,
or the signal is some spurious glitch, while other regions
of sensor reswitching (normal) activity are slower and
have curvature etc.

I'm not convinced the lean spikes are real, just looking
at the scan. Are they attended by anything the butt-o-
meter can sense (a cough, drivetrain jerk, ...)? Or are
you chasing a ghost that doesn't affect anything?

my wideband is logged there also. Both narrowbands and my wideband show the lean spikes, and the truck falls flat on its face when it happens.

I am full open loop in that log there......was only logging the narrowbands to weed out any false wideband readings since I just installed it. It will also do it with the O2 sensors completely unpluggged and turned off. It does it on MAF, SD, OL or CL.

[lwrs10]

Please help?

[lwrs10]

Thanks for all the help. And just in case anyone wants to know the fix, it was the injector offsets. They were correct for a returnless system, but not return style like I am using. Return style systems use a flat number across each voltage. It does not vary with KPA. I did not catch this due to my experience level.

[ViaBellator]

Glad you figured it out....and that is good information for the people that have custom fuel systems setup.

[smallblocker]

Hey lwrs10, I have a pair of basterd child s10's I'm ready to burn aswell. Both are express van 0411's, ones stock l31, the other 383, custom everything intake injectors. I was wondering if you have tackled closed loop op yet? I can't get either one to run correctly in closed loop because I don't have clue what I'm doing. Can I bug you for some info about you're swap?

Steve

[lwrs10]

Hey lwrs10, I have a pair of basterd child s10's I'm ready to burn aswell. Both are express van 0411's, ones stock l31, the other 383, custom everything intake injectors. I was wondering if you have tackled closed loop op yet? I can't get either one to run correctly in closed loop because I don't have clue what I'm doing. Can I bug you for some info about you're swap?

Steve

Send me a pm with some contact info

[smallblocker]

Hey thanks. Found another guy here with the identical problem, I'm reading up on how to post a log file.
Steve