My car threw code 23 few days ago. I find it strange because the Holley 670 I have does not have mixture solenoid. I was advised to start a new thread with pictures. Looks like my distributor is aftermarket MSD Street Fire HEI. Previous owner said the engine builder tuned the car to run mechanical advance. Other thread I had a member say it can be shorted wires on ecm. The code 23 has not change how the car runs. Thank you.

 

Without the original distributor and carburetor the ECM is doing absolutely nothing other than maybe controlling transmission torque converter lockup if automatic.

 

It is automatic th350. So I can just ignore that light? As long as it’s not affecting drivability of my car. Thank you

 

Thanks for the extra photos! I couldn't see that your distributor had a vacuum advance can before. That confirms that it is not a stock 81 replacement, and the ECM is not doing anything to control either the carb or distributor.

If your car is running well, and you are happy, just ignore the check engine light. Or remove the bulb! Some folks remove the entire ECM, and figure out another solution for the transmission lockup. Adding a third pedal is probably the best long-term solution for the transmission issue.

If you are running that car on the street, whatever the PO's intent may have been, you will likely be better off following @lars' timing and HEI installation instructions, and using the vacuum advance connected to manifold vacuum. Your can has a hex on the face, and should be internally adjustable. Limit it to 10-12 degrees of vacuum advance, as long as your engine makes vacuum at idle in the appropriate range (if you have a very aggressive cam, you may not have enough vacuum at idle, but you'd probably notice that). You will need to re-clock the distributor and vac advance, but Lars' instructions will cover that. You'll need a timing light and either a vacuum gauge or a Mity-Vac to do the rest. There is a learning curve, but the improvement can be dramatic. My stock 79 auto was completely transformed by following the Lars tuning method.

 

phew.. thank you so much for clearing this up. I disconnected ECM today. Man.. this car needs lots of work. I'm going to put another thread on carb/running rich.

 

I'd research alternate solutions to get trans lockup, or plan for a manual swap.

But in the meantime, no check engine light!