Upstream O2 Sensor Bolt Hole Thread

2009 Tacoma, 4.0L, "new to me" and it came to me with no upgrades. Threw a P0031 code. Got new Denso O2 sensor

$131 234-9067 Air Fuel Sensor

234-9067 (upstream driver's side). Thread size M18-1.5.
Removal was problematic of course. PB Blast used liberally. O2 socket and it "opened" up from wrenching on it so hard. Had to commit and cut off wire to use 7/8 impact socket with pipes. That got it off, but the damage was done. Male (sensor) thread material was in between the female (bolt hole) threads. Got some out with pliers, but top of bolt hole threads are all gummed. Tried picks, heat, PB blast soaked rag overnight, nothing would get that metal from between the threads.
So, committed again and started to tap using M18-1.5. I've Never Tapped a Bolt Hole Before (let the snickers commence) AND of course, can't catch the bolt hole threads with the tap. It cleaned out a lot of the lumps of metal, but smoothed the top threads. Trying to very gently, back and forth, ease it down to catch the bolt hole threads but nothing happening. I'm still pretty much on the taper of the tap.
Options? If I just jam on it will it screw up the rest of the bolt hole thread? Can you drill out, tap and use helicoil or will different metal type screw up the readings from the sensor? Tow it to the muffler shop?

 

It sounds like the first few threads are toast if I’m understanding ya. You may need to smooth those out, or maybe try a bottoming tap to help it grab

 

It's a tough one, an exhaust shop might be able to fix it. Anything you do will only make it worse. A professional O2 sensor thread chaser may fix it.

 

Definitely try a bottoming Tap or a thread chaser

 

Isn’t a tap the same size essentially a thread chaser?

 

A tap will cut new threads if not properly timed.
The chaser is more of a form tool to clean and form the thread.

What type of tap do you have?
A bottom tap has very little tapper at the start. Basically cutting to size right at the start.
A conventional gun tap has a longer lead and may be able to align or start past the damaged threads. Basically doing a ruff cut and finishing dia further up the tap.

The chase tool may be a good start I believe they are smaller dia at the start and grow to desired size. It also has less shank so it won’t go past threads and lose timing.
I’m a machinist and do this crap daily.
I bought the chase tool when I did my sensors.

If you end up drilling oversized and re tapping I’d use a thread sert over a helicoil.
Basically a piece threaded ID and OD.

 

Well, I had to drop back and punt. Didn't have time to mess with it any longer, so had it towed to an independent muffler shop, and he just banged it out with a thread chaser tap. Professional with years of experience vs a hack like me, that's not even an argument.

PS... I'll get another crack at this though! The code never cleared! The shop told me I put the sensor in B1S2 instead of B1S1. (The hack lives to shred another thread!) Thanks for the advice gents! I'll try again later.

 

Having the proper equipment makes a huge difference. Don’t be hard on yourself a lot wouldn’t have attempted doing it them self’s.