O2 sensor blow out!

[mbclay21]

Folks,

I have 1992 FJ80 3fe, and yesterday I pulled out into traffic and had to floor the gas (which I never do). I heard “thunk” under my seat and then the exhaust sounded like someone drilled holes in the muffler.

I pulled over and found the Driver side O2 sensor hanging by the cable (see picture) - it literally blew out of the bunge.

CEL did not come on and it drove to the house with no new issue other than the loud exhaust. I’m assuming my cats are clogged and pressing the gas hard created enough pressure to blow the sensor out. I will eventually be straight piping (cat delete) but I’m considering rethreading the bunge studs and putting all back together until I can spend some more money on new o2 sensors and some straight pipes.

Should I be concerned the CEL has not come on with the O2 sensor dangling outside the bunge?

Is it ridiculous to think the O2 sensor could work a few months in light driving situations until I can straight pipe?

 

[Nightbrew]

This happened on 96’ lx. More or less the nuts disentigrated.

 

[Rifleman]

Get some new nuts, new gasket, wire brush the studs clean of rust, next apply some copper never seize on the studs and then reinstall your O2 sensor.

 

[inkpot]

I would guess the nuts failed. Reinstall and test.

 

[Nightbrew]

After my nuts failed I determined that the studs couldn’t be saved. I tack welded the sensor on for a temp fix. Then I sprayed pb blaster on them every other day for 3-4 weeks so I could get them out with a pipe wrench. I replaced them with bolts to make future work easier. Coated them with anti seize before installation. So far so good.

 

[thatcabledude]

Unplug the sensor and ride out until you do your exhaust. Will not hurt.

 

[mbclay21]

I went with Rifleman’s approach.

Only catch was the studs had some serious “plaque” on them. Wire brush didn’t work, wire wheel on drill didn’t work. I had to run a die down the studs (autozone tap and die set) so I could get new nuts on them.

Size for studs and nuts is M8 - 1.25 if anyone runs into this issue in future.

Thanks to all!

 

[Qball]

Folks,

I have 1992 FJ80 3fe, and yesterday I pulled out into traffic and had to floor the gas (which I never do). I heard “thunk” under my seat and then the exhaust sounded like someone drilled holes in the muffler.

I pulled over and found the Driver side O2 sensor hanging by the cable (see picture) - it literally blew out of the bunge.

CEL did not come on and it drove to the house with no new issue other than the loud exhaust. I’m assuming my cats are clogged and pressing the gas hard created enough pressure to blow the sensor out. I will eventually be straight piping (cat delete) but I’m considering rethreading the bunge studs and putting all back together until I can spend some more money on new o2 sensors and some straight pipes.

Should I be concerned the CEL has not come on with the O2 sensor dangling outside the bunge?

Is it ridiculous to think the O2 sensor could work a few months in light driving situations until I can straight pipe?

View attachment 1883438

View attachment 1883439

Is it me or is that O2 sensor freakishly clean and lack the typical black carbon deposits?

 

[inkpot]

Use copper nuts from VW exhaust system for longer life.

 

[JeepinPete]

23 years of life using the factory hardware, I don't think longer life is really required

 

[decoco]

So is that the reason why this O2 sensor blowout happens? Pressure buildup at the cat?

I had this happen to my fzj80 at about 146,000 miles, less than 2,000 miles after I bought it going through a mountain pass.
Lots of loss of power.

I was new to working on cruisers and cars at the time so I saw the O2 sensor hanging like in the picture, took it to a shop, and the guy at the shop said he welded it back on. Truck has worked fine since then but I often think of replacing the o2 sensors as PM.

 

[Tools R Us]

So is that the reason why this O2 sensor blowout happens? ...

In most cases the nuts rust away.

 

[Tools R Us]

23 years of life using the factory hardware, I don't think longer life is really required

What is the assurance that the hardware/sensor is original? My guess; that hardware has not been serviceable in a longtime? In rust bucket areas, the copper nuts remain serviceable much longer and are easier to deal with.

 

[mbclay21]

Thanks, Rifleman, that’s the route I took. Only issue was a wire brush wasn’t enough to get the material off the threads. I even used a wire wheel on a drill. I ended up having to run a die over it to get the threads in shape for a new nut.

The only threads that weren’t boogered up, were the threads at the base that would have been covered a nut. With the threads above that point completely impassible by a nut, it looks like the original nuts must have just disintegrated or split and fallen off. There was no trace of them.

 

[mbclay21]

P.s. I drove about 50 miles today around town with no issue. It drives normal, sounds normal, and no codes.

 

[amgraham]

I had that suprize too a few weeks ago walking back to the truck and noticed the sensor hanging. I had to run a die on the studs and use a smaller nut but it seems to be holding fine.