I replaced the O2 sensor on my '93 Loyale this weekend. It went much easier than expected. The hard part was figuring out how to disconnect the connector, the scary part was if I had a 7/8" ring wrench tight enough to fit the corroded old sensor body.

 

In the end, it practically fell out in my hand. I could have pulled it with a crescent wrench.

 

I replaced the sensor because my gas mileage has been dropping for the last few months. The best it has been getting is 13 km/l, it used to get well over that on the highway when I keep the speed moderate.

 

The old sensor had soot deposits on the base. Is this typical, or is it a sign that my engine has been running rich?

soot is very common in the ones i've pulled, i wouldn't relate it to any issues. they're almost always black as well as that "burnt white" look when i pull them.

it's exhaust gasses. soot is typical. youll find it all along your exhaust system.

 

now if it had unburnt gas on it i'd say its running rich:lol: