Changed forward o2 sensor.

154040 miles

Current Avg MPG before new o2 sensor install: 17.4mpg

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Part Number: Denso 234-4154 Oxygen Sensor(i think or Denso 234-4162, those are the 2 I bought for before and after cat)
Amazon.com: Denso 234-4154 Oxygen Sensor: Automotive


OEM nuts (part number 90179-08059) x 4

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Been sitting on the forward o2 sensor for awhile and finally got around to trying it. I didn't have codes or anything, just working on maintenance stuff. I read removing the plug was going to be real pain but it was actually really easy. My o2 sensor was missing one nut. I broke the other nut/stud trying to remove it. Next time heat it up, I can't believe I forgot. But I used this

Irwin Industrial Tools 394001 Bolt-Grip Bolt Extractor Base Set, 5-Piece - Bolt Extractor Kit - Amazon.com

And it really gripped the old rusted nut... well too much, I think I used the 13mm one (doesn't come with the 12mm). It took the whole stud with it. I figured I was only running with 1 nut for awhile anyway. I'll see how this goes. If it leaks or I get codes I'll get it welded. I was thinking about putting steel worm-clamps on it too if it becomes an issue. And I anti-seized the crap out of the one nut on there.


This pic really helped to remove the plug



taken from 4x4Wire - Tech: Time to Replace the O2 Sensor on your 3rd Gen Toyota?



With a small screwdriver, seen in the next image, with my feet dangling out the passenger side, looking over the exhaust I used the small screwdriver to pry the latch up. Very easy. I used a flashlight to highlight the area. Didn't remove any bolts. Took 15 seconds once I saw the picture above.




old o2 sensor and small screwdriver to remove the plug.

So far so good. I probably should have disconnected the battery. But i think it's improving. Not as sluggish anymore. I'll update later with mpg and experience.