99 5.7 vortec 383 closed loop issue

[Arkie]

I just bought a 383 GM performance motor from a fellow rockcrawler. Ran great in his rig but he needed the LS?

After the swap runs rich once in closed loop. Replaced all sensors. No change. Replaced O2 sensors. No change.

No vacuum leaks.

Only running bank 1 sensor per bank.

Bought a this scanner. O2 voltage looks normal in both banks until closed loop the. Bank 1 high (.9) and bank 2 low (.05). Once in closed loop black smoke.

No codes.

Unplugged O2 sensors and it runs fine.

It ran fine until we pull led and reinstalled in my rig.

I have read about all I can find about this and I?m stumped.

Any thoughts?

Thanks! J

[5FDP]

Well you can't just toss a 383 engine into your truck and expect it to run correctly on a stock 5.7 calibration file.

It's more cubic inches, much larger camshaft. If it came with an intake and injectors that are different than your stock spider injectors, that will also make it run worse.

[Arkie]

I agree. I also swapped in the donor computer. Ran fine in his rig.

It runs great in mine in open loop. I?m trying to understand the one bank lean and one rich when in closed loop.

[2xLS1]

O2s crossed

[Arkie]

Harness is too short but I'll break the loom apart and try it...

[2xLS1]

Just unplug one bank and see if that bank goes to 450mv on the scanner.

[Arkie]

Roger that. I do know they both sit at 450 when unplugged. Bank one should be on the drivers as that is the same side as Cyl 1... Correct? I am taking notes.

Thanks for the help!

[2xLS1]

B1S1 Drivers side pre cat
B2S1 Pass side pre cat

[Arkie]

That was it! Had to relocate the knock sensor and the b2 was in that loom… swapped it around. Thanks a million! -J

[Fast4.7]

Buddy managed that on his 6.0L swapped 97 I tuned. Ran terribly with the 02s swapped. It would quickly trim the fuel trims on each bank to lean and rich limits.