FAQ: Lambda/Oxygen Sensor

[Welly]

AGAIN SHOULD NOT BE IN THE FAQ SECTION - NOT LIKE THIS ANYWAY
NEEDS TO BE A QUESTION FOR A START AND AN ANSWER

Installed in the exhaust down pipe these sensor's measure the level of unburnt fuel in the exhaust stream and feeds this back to the ECU to help control fuelling (closed loop mode operation). A failing sensor does not always cause a fault light as its' sensitivity fades slowly over time. Symptoms include poor fuel economy, running rich. Can cause mid range acceleration 'lags' where the engine feels like it is hesitating slightly only in mid range (also hesitates coming off the gas too). Lambda/Oxygen sensors are designed to fail; they need replacing every so often (5 to 7 years). Best to replace with genuine sensors as some universal type oxygen sensors have been known to cause problems …

I had a feeling there was a little over fueling and did a check with no record of my sensors being replaced, knowing that there a serviceable item Ive had them replaced and what a difference its made to the engine, pickup has improved as well as the economy...no lag in mid-range either now or when lifting off the throttle....