Replacing an oxygen sensor

Since last fall or so, the car has been getting really rubbish fuel economy. Our Fabia has never been right on the cutting edge of economy — ours is one of the last years that Skoda continued to use a block designed in the 1970s — but it used to do much better than it has recently.

I’ve been trying to figure out what’s caused this dropoff, slowly working my way through the car piece by piece. I’ve replaced the oil, ensured that the tyres were properly inflated; then I replaced the spark plugs: the previous ones were improperly gapped, but the new ones did not solve the problem.

On Wednesday, I jacked the car up and replaced the oxygen sensor behind the catalytic converter. Aaaaaand it has not made a difference. Still, it's given me a bit more confidence crawling around under the car, which isn't valueless. And I also learned a futile lesson in taking apart and repinning a plug.

Next up: the front oxygen sensor.