Another question, are we talking the ECU or Bosch engine control unit located in a black plastic box on the left fenderwall?
On these cars, they don't control the ignition. They are for fuel managemment mostly on the K-Jetronic system. It is important to match a four cyl Lambda Sound (O2 sensor/frequency valve )model with what is on the car, OR what was put in your car. There is another one for cars equipped with EGR, and still another one for a six cyl, which I believe all US models had the Lambda Sound system.