I'm having an issue with the bank 1 short-term fuel trim oscillating from 110-125% at idle as you can see in the photo while bank 2 is staying right around 100% as it should. I have brand new 1300cc injectors installed so I doubt it's that. I also fixed an exhaust leak issue and confirmed it with a smoke test. Does anyone have any idea what could be causing this?

causing this?

 

I have the exact same issue did you ever figure it out?

 

You are the only person I have found with this exact issue so if you see this please reach out because I have been trying to fix this issue for months.

 

Have you gone for a drive and checked these same trims. Being that you have smoked checked for exhaust leaks we can remove this from it being the fault.
Cats/HFC/Test pipes?
What are your vacuum numbers at idle?

You should record logs at 1/4 and 1/2 throttle to be able to obtain more data.

You should also try to pinch while at idle:
The evap line
PCV 1
PCV2
Breather 1
Breather 2 to check for variances.

Swap MAF from one bank to the other.

Lastly, though you said New injectors it doesnt necessarily mean they are ALL spraying evenly. Unless the injectors were sold as a flowed and matching set you can never truly remove these from the equation. It's detecting a higher count of air so it richens the exhaust to compensate until it hits 125% which is max and then it has not choice but to force it, it then detects a lower % which then it tries to switch back to a normal fuel trim but since the problem persists it goes up to 125%.

It's possible that there is a leak of air somewhere in the system, pinching hoses and or temporarily removing the PCV/EVAP/Breather as long as the TB and manifold gaskets are good you should be able to see a more even number which will point to those hoses.
Since aftermarket injectors were installed, it's possible you might have a pinched injector seal that creates a vacuum leak That same smoke test could be used for the intake side. Start with that.

 

can’t go for a drive because car is on a base tune atm but the trim does even out when I give it some gas. I think I will start by checking injector seals. Because my tuner said if it was a vac leak in the intake system it would show on both trim’s because they share air. And that would make sense because the guy who has the exact same issue as me replaced is injectors as well that’s the only constancy I’ve seen.

 

Injector seals is a good one, you can spray some starting fluid/carb cleaner around the injectors at idle and watch your short terms over time , if they go negative that would be indicative of a vac leak.

02 sensor could have decided to die as well.

 

Edit: Sorry if my comment seems confusing. I had a similar issue and i made a post with the smae title on The370z forum.

Thanks for the suggestions. I found my issue to be swapped ignition coil plugs between cylinder 3 and 5.

 

you just swapped them and your issue magically fixed?

 

I had the plugs (wiring) swapped. So the ECU would tell cylinder 3 to fire but it was really firing cylinder 5 and vice versa.

 

hmm interesting I haven’t touched those but I did install new injectors maybe I have the connection in the wrong spot. Do you have a pic of your stft line graph when you had the issue?

 

 

Though similar in pattern. @projectpanda13 trims actually go from 100-125% where as OP trims stays between 110-125% this leads me to believe the leak is significant.

To add, though both banks share air path ways, an air leak in the bank 1 side injectors would be so close to the valves that it would have very little effect on bank 2. Injector seal air leaks are the least common air leaks in these engines which is why there is little graph info on this.

The smoke test of the intake manifold will yield maybe more than one. The initial fault and maybe a baby leak.