I have a 99 Beetle with 100k on it and it has a service engine code stating it needs another O2 sensor (i just replaced the same one 30K ago). It also has stated in the past that it has a random misfire in which the mechanic has told us is common and would go away with xxx.. amount of turns to the key switch. Sure enough the misfire code goes away but when the O2 sesor code is on the fuel economy is terrible!! My own reasoning tells me the two are related and I should have the ignition coil checked or something else but could use someones knowledge on this subject!

Any help greatly appreciated!

TandG

 

I think you should take suggestions from trained mechanics then get upgraded with these kind of after market upgrades.

 

An oxygen sensor is a chemical generator.It is constantly making a comparison between the oxygen inside the exhaust manifold and air outside the engine.If this comparison shows little or no oxygen in the exhaust manifold,a voltage is generated.The output of the sensor is usually between 0 and 1.1 volts.All spark combustion engines need the proper air fuel ratio to operate correctly.