Faulty Lambda Sensors Increase Pollution

NGK Spark Plugs, which manufactures lambda sensors under the NTK brand name, recently commissioned an independent expert report to determine the impact of a defective Lambda sensor on the output of toxic emissions and fuel consumption.

Carried out by TÜV Nord, the test involved a 1993 VW Golf III following the European test cycle according to guideline 70/220/EWG. Three road tests were carried out with an active Lambda sensor, followed by three more with a disconnected sensor and the output of emissions and rate of fuel consumption were monitored.

A massive increase in toxic emissions was recorded when the engine ran without the sensor – the engine control unit was missing vital information needed to control the air/fuel ratio and the catalyst was unable to correctly convert the pollutants resulting from the combustion process.

Carbon monoxide output alone increased eightfold – a particularly serious problem in urban areas, as the poisonous gas is heavier than air and concentrates near to the ground, posing a possible hazard to children in particular. In addition, the level of hydrocarbon emissions increased by a factor of 2.5. Fuel consumption was adversely affected – with the “failed” sensor it increased by an average of 10 per cent, with even more significant increases in urban traffic.

NGK claims that these are the first fully independent tests of their kind and, while it is not certain that the results would be repeated on other vehicles, it seems likely and demonstrates the need for regular checking of Lambda sensors.