Rich in one bank, lean in the other, equal on load

Pete fender

Pete Fender
So.........Is the eec 4 & 5 batch fire or sequential?

FWIW - we had a 5.3 ls on the dyno once in full sequential setup. Was for my buddies efi class. He was showing the students how to test the injector inputs with a noid light. We randomly picked a cyl and told the ecu to test fire thar injector but nothing. We quickly learned in front of the class our dumbasses crossed the wires late night getting ready.
I can promise you when we fixed the issue. The motor repeated its self on the dyno with two crossed injectors just spraying fuel on the back of a closed intake valve. The motor didn't care.
I've tried both ways on my personal engine on the dyno and that alone makes no power difference including various injection timing changes throughout the rpm range.
There is however a bit of power to be had with individual cyl fuel trims which can only be had with sequential.
Most of what the oem does is all emissions and fuel economy based imho.

I just thought of something.
Your motor may be batch firing, causing one side to be richer than the other, since that is a dawback of the older batch fire systems.
Check the plug on your Cam Position Sensor, make sure the plug is intact.
Then trace the wires to that plug as far as you can, they may be pinched or internally broken inside the insulation.
Or caught up in something.
Also check any fuse that goes to "GEM"
General Engine Management.
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Chris Henderson

New Member
Pete maybe on to something with the wiring. Its gonna be something really stupid when you figure it out! Lol

Could even just be an exhaust leak letting air in the pipe. O2 sensors are very sensitive. Did it to myself once with slip on collectors........

Pete fender

Pete Fender
Exhaust leaks cause problems.
Mostly where the header meets the down tube, a leaner mixture on the side that leaks.


Active Member
Sorry for the very, very late reply everyone. It took a long while to get the car to the mechanic because his calendar was full, but he went in, looked over all the work he had done previously, but found no faults and couldn't see any other issues. He recommended going to someone who specializes in finding issues with these. However, I've been working with 6 Shooter on some tuning and with our tunes we're not quite seeing the issues the Bama tune was. This makes me woner if they were just being lazy and throwing an OTS tune on there without minding all the info I shared with them. The car is currently being caged, but as we get the tune closer and closer to being complete we'll have a sure answer whether it was literally just the tune or if there still is a problem. All I can say is if there's an actual issue, it's going to be expensive to have someone find and fix.