I found a 79 zx that had been stored indoors for 25 years. The owner said it stopped running so she parked it.
Put a new battery and gas and drove it 40 miles home. It would not idle below 1500 rpm. The bcdd clicks when I hook up 12 volts to it. It has the wire coming out of it but not hooked up to anything. I put a new AFM in it and it runs extremely rich, tried another AFM with same result. New vacuum lines etc. It did not run rich on the 40 miles home. The rpm came down to 800 or so, but rich to the point of plug fouling. Any ideas on this issue ? Seeing how its almost 40 year old equipment.
Or 2, is there anyway to upgrade to a newer FI system ? What are people doing to keep them running ?
I would like to keep it as simple as possible. thanks for any input Steve

Forgot to mention. I think the computer is going to a default mode . Been sent a bad control to run rich ?

I know very little about the ZX but in the past I've read of problems with a temperature sensor. Often it is replaced by a potentiometer. Google is your friend.

How about the throttle body? is it closing completely? IIRC the 79 uses a weird air bypass on the bottom of the TB to regulate idle. Forgive my I never messed much with the pre 82 injection.