Anyone ever figured out split BLM’s on 92-93 batchfire
 

Ive always had split BLM’s on my modd 93.
Ive looked everywhere for false air sources, (leaky vacuum ports), etc - to no avail.

since i cant adjust individual cylinder fuel trims, the best i can do is avg left and right bank together to ‘split the difference’ and tune that way

Anyways wanted to see if anyone has any ideas on how to correct split blm’s

No exhaust leaks?

Nope.

have installed headers a couple times and have always had split blm’s

even re-did the o2 wiring hArnesses - got rid of soldered extensions ( solder apparently a no-no on o2 sensor wires).

even found/installed NOS 1996 vintage ac delco heated o2’s (vs. todays made in china ac delco o2’s or bosch o2’s)

no dice

GM did, as they went to sequential EFI after 93... Other than that I personally changed every fricking item on my LT1 396 and LT1 350 to no avail. Several tuners, different headers, injectors , manifolds, gaskets, throttle bodys, converted to heated O2s etc etc etc.. Nothing.
But with a wide band O2 sensor reading left and right headers during idle etc, nothing was wrong..

Haha. Yeah i did all that.

Best i can do is take an averAge (btwn left and right) and set VE tables to ‘split’ the difference -make one equally rich / and fhe ofher equally lean . At least according to the o2’s.

Yes, set your tune as open loop

:iagree:

That takes skills I dont have right now. But, if someone has a tuner that does this, it would be nice.
On a side note, who is at idle that long anyways

I would suspect an injector calibrated somewhat different or O2 sensors that didn't match (calibration). If I really wanted to "see" what was going on, I'd consider swapping in a wideband or even a sniffer (like you find at a roller dyno). Then, which ever is closer to the dyno, use that O2 reading for tuning. I wouldn't be surprised if differences in scavenging (between banks) could contribute to imbalance...in the absence of other exhaust issue.