ls3 swapped f body decel fuel problem

[TheGreenBastard]

Ive been trying to correct a dyno tune that i paid entirely too much for. On decel in dumps so much fuel into bank 2 and i cannot figure out why. Ive turned on dfco because for some reason it was disabled during tuning but i dont see it doing anything. Ive also changed the entry and exit RPM map vs baro back to the stock values ( they were at 1900 and 1200 i think). Is this in the dfco or should i look elsewhere? Seems like nothing has been right with this tune.

Thanks guys.



edit* I know volume is incorrect, but when i made changes suggested on here ( ls1 to ls3 conversion and volume change) the car didnt like it so i have to revisit that when i figure out some of the other problems in the tune.

[Frost]

Bank2 has an issue and it is NOT your tune; it's your car. There is a point where B2 is adding 47% total and B1 is 2%. You can't tune one bank to be leaner/richer than the other. Check for a vacuum leak around the injectors on the passenger side.

[Alvin]

Agreed 100% a mechanical, wiring, or sensor issue. I've been seeing a lot of stuck injectors on Gen 3 applications recently. Bad IAC's for that matter too.. seems like about 20 years is what you get out of them lol.

[TheGreenBastard]

Went around with injectors with propane and found no change in idle, the car has had this problem since the crate engine has been dropped in so I wouldn’t think it would have any problems with injectors or leaks but it definitely looks like it. To add, I’ve changed plugs and o2s and a known exhaust leak, but that was on the driver side. While I’m thinking about it, could a burned wire going to the o2 cause this?

Thanks for the input guys.

[TheGreenBastard]

Double checked no wires were actually burned, I’m stumped. I’ll swap injectors side to side tomorrow and see what that does. If it’s not that it has to be in the wiring I think, wouldn’t even know where to start to diagnose that.

[blindsquirrel]

O2 sensors wear out over time. If you don't know their history, just replace them so you know you're starting fresh. Use only NTK or ACDelco sensors.

[TheGreenBastard]

I swapped the o2s the other day for a different pair and it was still showing that side adding fuel. would a plugged injector show in the pulse width? This is adding to my confusion as well, i can give it 2 percent throttle and its okay, but as soon as i let out it throws +25% ltft instantly for bank 2.

Attachment 106656

[TheMechanic]

Plugged injector will not show in pulse width. Check for misfire codes or current misfires. Also you could selectively disable injectors and see if you have a cylinder not contributing. Personally I would test do a simple pressure drop test. It is pretty simple but you will have to purchase an injector tester. They are pretty cheep. Many ECM/PCM's have them in the software. Basically you install a fuel pressure tester, record the pressure (needs to hold pressure) then you pulse the injector and record the pressure drop. Do it for the remaining injectors. I will normally not have more than a 3 or so PSI DIFFERENCE between any single injector. Most of the time it will be readily apparent. If the engine has a fuel pressure regulator that is referenced on manifold at the fuel rail they often rupture the diaphragm resulting in raw fuel getting dumped in the intake. Of course that usually results in negative LTFT's.

[TheGreenBastard]

Just did a run up to check misfires and coils a couple of minutes ago and everything shows good. I have also disabled each injector and looked for the drop in RPM and all dropped roughly 50 rpm or so except for one which didnt seem to drop as much to me. Maybe partially plugged? Ill definitely look into getting an injector tester. I do have one DTC but i didnt think it was related. P1637 - Generator L- Terminal circuit.

[TheMechanic]

Gen L is common. Like I said many GenIII and above have injector pulse for this exact diagnosis. Maybe get someone with a better scan tool or an MDI with Tech2Win. It will be there. You can pick up the ones that hook directly to the injector for around $30. Funny because I literally have well over $1,500 in injector pulsers. Hahahaha

[TheGreenBastard]

I looked a little closer look when turning off my injectors, when I turn off 6 and 8 bank one it starts to add fuel, wouldn’t that mean they’re swapped somehow? I don’t know how bank one would be okay majority of the time though.

[TheGreenBastard]

Found the problem, there was a hole in the top of exhaust up against the bottom of the car, downstream from the o2 that was pulling fresh air.