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1995 Taurus Code 172

I am back with another problem with my 1995 Taurus SE with OBD1! The last time I got a lot of help from cigroller and 87 Ranger and others!
The diagnostic trouble code is 172. It says, "Lack of Heated Oxygen Sensor (HO2S-1) switches, indicates lean (Bank #1).
What does that mean and what can I do to correct it?

It could be the O2 sensor but don’t start replacing things blindly. An O2 sensor is not really cheap and are also kind of a pain to replace so save that for last.
They do go bad but it could be many other things.

Since it is a lean code, I’d check to see if you have a vacuum leak somewhere. First look around for cracked hoses or for hoses that may have fallen off. Vacuum leaks can be detected by carefully spritzing starter fluid around vacuum hoses while the car is idling. If the idle changes (usually it will pick up), the starter fluid is being sucked into the air intake near the spot you just spritzed. Look around - you’ll likely find a crack or break.

I checked all those hoses and found only 1 hose that had slipped out of place a little but I don’t think it was sucking air. I clamped it! The check engine light does not come on right away, comes on after the engine is warmed up! The engine runs pretty good but seems like it is in high gear when it should be in second. What should I do about lean bank #1?

I replaced both heated oxygen sensors. I am as sure as I can be that there are no vacuum leaks. It runs a little bit better but still feels as if there is not as much power as there should be. The check engine light comes on later but still comes on. I reset it by disconnecting the battery ground. What do I do now?

I should also say that it still shows the 172 diagnostic trouble code.
I did blow out a small amount of internal honeycomb material from the catalytic converter when I replaced the gasket between the big manifold pipe and the flex pipe. I also replaced the flex pipe at that time!