The Mighty 258 > Fuel Systems.

Non-stepper BBD running rich

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jeepneagle:
I'm getting my 84 Limited wagon back on the road. PO replaced the feedback BBD with a rebuilt non-stepper unit. I'm trying to get this thing tuned, but it runs rich at cruise. Here's what I've done:

Removed CEC system
Rewired ICM to bypass computer
Routed vacuum lines to pre-CEC configuration (vacuum is 18in at idle)
Reset base timing to 10°BTDC
replaced vapor canister
replaced fuel filter and hoses
adjusted choke and high idle to factory specs (works great and opens fully when warm)
Tuned idle mix to 14:1AFR

My problem is when cruising my AFR drops to 12:1. I adjusted the metering rod step-up piston to .040in and the accelerator pump to .500in as per te TSM and reset the metering rod lock screw to no avail. I even tried turning the adjustment on the step-up piston counter-clockwise another turn which should lean out the mix, but no dice. Every time I adjust the metering rods, I redo the lock screw like the manual says. What else would cause a rich condition when cruising?

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