Just checked green & black code connectors on a 90 legacy I just bought found they have been connected all this time,don't know how long does anyone know what effect this has?

Welcome to the USMB.

 

There shouldn't be any issues with them being connected.  With them connected the ECU just won't likely retain the long term fuel trims.  With them disconnected you may see an increase in fuel economy.

Not sure about having the green hooked up, but on my '94 I noticed with the black ones hooked up and no codes the CEL flashes continuously.

All that will happen is that the computer will continue to clear any code that shows up.

 

Once the plugs are all disconnected you may find that you engine throws a code.

 

TOONGA

Simply disconnect them and drive the car. There should be no lasting ill effects.

 

If the CEL comes on, follow the directions to read the code(s) found here

Correct whatever problem the code(s) may indicate

 

Just make sure to disconnect the test connectors when done.

 

The 1990 is pretty forgiving and an easy car to work on.

I want to thank everyone that replied to my post u have all been very helpful,it shows most of us can rely on each other for help at times of need,blessings to u all. Thanks Dave S.