Alfa Romeo Repair: la mbda sensor +spark light, lambda sensor, sensor light

Question
the car started cutting out and the red sensor light would come on,it would get to stage were it would be chugging along and would stop,my wife commented it was like dirty petrol however it would not restart ,turning but not connecting,brought to garage and it showed a lambda sensor problem ,was replaced ,but mechanic not happy with power transmission,retested again and still showing lambda sensor problem,mechanic doesnt want to touch anymore
any ideas
david

Answer
The spark plugs are fouled. Also, you need to test the reference voltage for the O2 sensor: disconnect the lead to the sensor and attach a digital multi meter to the end going to the ecm. You should see a dc volt reading of 0.5 volts if all is well (with engine running or key on).