ENGINE NOT WORKING FINE

If you know one of the "PLUGS NOODLES" is not working why would you replace the "BRAIN BOX"? If a spark plug wire is arcing just replace them. While your at it replace the spark plugs as well. By "ONE OF THE PLUGS NOOZLES IS NOT WORKING" do you mean that the engine misfires? Or do you mean that the engine will not start? A misfire in one cylinder is usually caused be a fouled spark plug or a damaged spark plug wire. If those are fine the next item down the line that could be the culprit is an ignition coil. If it is an older 323 and has a distributor replace the distributor cap and rotor. ECUs are very reliable and tough. One usually does not just go bad unless someone wired something wrong while repairing an part or adding aftermarket parts that require you to tap into the vehicles electric system. I usually tell people that if you are not sure how something works not to try and learn on it. Best to leave it to the professionals.