Fuel trims opposite bank to bank

[cheezydoublebeefy]

Hello everyone (first post here so hopefully I don't butcher this).

I have searched for this issue, but either did not see what I was looking or or suck at searching, you decide.

I'm working on a customers truck that the LTFT are off side to side. At idle bank one read lean (adding 8-18%) and bank two is near zero +/- 5%. Off idle sitting still bank one will switch near zero and bank 2 will read rich (taking out 8-18%). I've installed new upstream oxygen sensors and swapped side to side (rears are non existent). I've smoked the intake manifold and had leaks around the fuel injector o-rings so I have replaced all fuel injector o-rings and intake gaskets. I do not see any kind of intake leak anymore and do not see/hear any exhaust leaks. I know it is probably something I am over looking, but have wasted to many days it is time to seek some help. Truck runs and drives fine otherwise.

Also maybe important to mention is fuel trims seemed to read better when virtual flex fuel was enabled (reading 60% ethanol, which it was not. I had filled up with 91oct a couple of times, but I know it takes time to adjust. After turning off virtual flex to get everything dialed in, that is when I believe I started to have fuel trim issues. (customer wants to switch to a physical sensor which I agree with)

We had a 2011 camaro with a spl blower in before with this same issue and I never resolved the problem and it feels like I am being haunted again.

Vehicle Info

2011 Silverado (was 4.8l)
E38 ECM-currently in maf only mode for maf tuning.
mildly built 5.3l (unknown specs)
Mild camshaft
stock truck intake manifold
procharger (10-15psi)
long tube headers (rear o2 deleted)
Injectors dynamics 725cc (id data transferred to tune)
gm 3 bar map sensor
snow performance water/meth injection (currently off until truck is dialed on 91 on dyno)

I also included the current tune and a couple recent street logs. (sorry no wideband on those logs).
I can include some logs on the dyno with wideband if requested when the virtual flex was still enabled.

Any help will be greatly appreciated guys!

[STAGEUP]

Swap your injectors from one back to the other and see if the issue follows. If it doesn't follow, do a compression test and that should definitely uncover your issue.

[Ben Charles]

Typically when I see this the 02 sensors are swapped

[MrMeany]

I would check to make sure injector harnesses are not crossed

[cheezydoublebeefy]

Typically when I see this the 02 sensors are swapped

I was really hoping for this one to be it, but when I unplug the actual bank 2 oxygen sensor a code for bank 2 sensor sets. So I don't believe they are crossed like I was hoping they were.

[cheezydoublebeefy]

Swap your injectors from one back to the other and see if the issue follows. If it doesn't follow, do a compression test and that should definitely uncover your issue.

Hello STAGEUP, We swapped all bank one injectors to bank two and still is the same. The compression test does show bank one a hair weaker than bank 2. Bank 2 is all between 140-150PSI. Bank 1 is hanging between 130-145psi.

[ngc1068]

Have you smoked the exhaust to see if theres a leak anywhere upstream or nearby downstream of the narrowband on that bank? I was having same problem and found a small exhaust leak on the rich bank where the collector bolts to the catback (the leak is about 3” after the narrowband on my setup, but I’ve read at part throttle it could suck some air between pulses) I’m waiting for a new gasket to arrive to find out if it solved my problem.

[cheezydoublebeefy]

***update***
So I have gotten the fuel trims a lot closer to zero after spending a ton of time with the vve and maf table, but still end up with bank one adding fuel and bank two subtracting fuel right before wot/open loop acceleration. Therefore the long terms are carrying over during wot. Also I am struggling with target afr, shortly into the pull and going into pe the actual afr "pegs" to 10.6:1 when the commanded is 11.3:1. I keep adjusting the maf table working with a afr error histogram, but I cannot seem to get a change. Am I overlooking other settings/tables that could be affecting this? Also I have included a log that shows funky o2 sensor readings during wot. Bank 1 bonces rich to lean for the first part of the pull and bank 2 just goes rich like normal.

I am sure I have made some bonehead mistake, any suggestions is greatly appreciated.

ngc1068 mentioned smoking the exhaust for leaks and that is next on my list of things to check.

Thanks guys.VVT ADJ 2.hptVVT ADJ 2 RUN 3 COOL DOWN.hpl

[mbray01]

What brand o2's, i would bet your fighting either poorly functioning o2's or you have an exhaust leak. A leak the size of a pin hole at the o2 bung can give 25% deviation in fueling.

[cheezydoublebeefy]

What brand o2's, i would bet your fighting either poorly functioning o2's or you have an exhaust leak. A leak the size of a pin hole at the o2 bung can give 25% deviation in fueling.

Both oxygen sensors are brand new Denso OE direct fit replacements (of course that doesn't always mean they can't be faulty).

I am going to swap o2 sensors bank to bank once again for fun and leak check the entire exhaust system.
I will let you guys know what I find.
Thanks.

[cheezydoublebeefy]

Hello guys, not trying to bring up my old thread, but I have finally figured it out.

I found cylinder number eight ignition coil to be firing, but extremely weak. I thought I would have picked it up on the misfire counters, but never had any hits and never had any misfire codes. Come to find out the last tuner has changed the tables to keep that from setting. I feel embarrassed that I didn't detect the misfire over the camshaft on the dyno, but eventually felt the miss when simulating pulling a trailer.

One new coil and fuel trims are happy. Thanks to all for your help.

[ngc1068]

What did u see to suspect a bad coil, how did you confirm the suspicion, and how did you identify which one to replace?

[cheezydoublebeefy]

What did u see to suspect a bad coil, how did you confirm the suspicion, and how did you identify which one to replace?

I did everything the hard way First it started with taking out the spark plugs to do a compression test. I found #8 plug clean as a whistle like it just came out of a box (truck just got new plugs before going on the dyno). I checked the ohms on the injector and checked the circuit with a noid light and all was good. Next I pressurized the fuel rail and pulsed the fuel injector with a special tool and recorded the fuel drop. All matched and now I knew the injector was working and the cylinder has fuel. So therefore checking the ignition system was next. I also noticed the exhaust runner temperature on #8 was 100 degrees Fahrenheit cooler in comparison. A simple spark test of arching the spark plug to the exhaust runner showed #8 arching, but was very weak. The other cylinders had a very strong arch and even gave me a good shock once lol. After the ignition coil was replaced the truck started up and ran smoother than it ever has. Also immediately the fuel trims were evening out side to side. Of course then I had to go back and retune my VE and MAF tables.