Buick 231searching At Idle????

I have a buick 231, Installed Howell EFI, starts, runs, drives, but searches at Idle from 750 down to 500 up to 1000. No codes, vacume lines are all new, no leaks, timings is good, ive checked for leaks with starting fluid no luck, replaced distributor and internals with stock rebuild. Did the same exact thing with Rochester dual jet prior to EFI upgrade. Any insight?

 

Try resetting idle air:
Idle Air Control Calibration Link......

https://www.gmcmi.com/wp-content/uploads/2013/02/TBI-Initial-calibration.pdf

 

Also check for vacuum leaks on the intake manifold.

 

Is it an even fire or odd fire 231? If it's odd fire, you'll need to add a crank trigger for a smooth tach signal to the ECU.

 

...and I missed having the same issue with the carb. As others have said, check for vacuum leaks. Also checking compression and if all the rocker arms are moving the same amount could be worthwhile.

 

When checking for vacuum leaks, don't forget the heater controls if that is still hooked up. When you timed it, was it consistent? Could be a timing chain issue but I would expect that to be evident throughout the rpm range.

 

I am still sorting my stuff out with a searching idle, but found an Amazon smoke machine extremely helpful looking for vacuum and exhaust leaks.