[RustyLugNut]

If it is sluggish but operating, you can use most of the techniques used in the catalytic converter cleaning thread. The only difference is you don't have to worry too much about your molar strengths as you don't have to worry about stripping precious metal catalysts from your substrate. You just have to clean off the ceramic that forms the Nernst Cell circuit.

Start with a sodium hydroxide cleaner commonly found as " Purple Cleaner ". This will strip your caked on hydrocarbons and varnishes in short order. Dunking the sensor in gasoline may take a long while (over night) to get any effective cleaning and it may not dissolve carbon deposits effectively. Warm up the Purple Cleaner to just below boiling and set just the tip of the sensor in the liquid. Less than an hour is usually more then enough.

Then you do the same with a strong acid solution. Most any acid will work other than Sulfuric Acid. Sulfur can form a difficult to remove deposit. Muratic, Citric and Oxcalic acid, which I prefer, have proven effective. A warm solution is all that is needed. Dipping the sensor tip into the solution for an hour is enough to dissolve metallic build-ups and deposits.

Rinse and test the sensor using the propane torch and DMM procedure and you should see an improvement if the sensor is still in good operating condition.

I have successfully cleaned over two dozen sensors, both narrow and wide-b and.