failed emission test, too much polution Options

[celestrial_rider]

so my '94 celica gt failed its emission test again (2nd time) this past week. it gave me the same reading that im making too much CO. i changed the oil, oil filter, air filter, sparkplugs, even poured in a bottle of seafoam into a full gas tank..and it still fail. i was given a few options b4 my next emission..either i replace the knock senser, or replace the O2 senser (a buddy recommended either, or both). just curious if u guys can piont out anything else that might b causing this high level of polution..just anything. thanks.

[bindertch]

High CO also can show a bad converter if there is also high NOx and high HC. Yes high CO will indicate a rich condition but there would be an issue with fuel consumption being up. If you want to confirm what is causing it you should take it to a shop that has the diagnostic equipment to see if an injector is sticking or if the O2 sensor is indicating a lean condition all the time. If your fuel mileage hasn't changed then I would suspect the converter.