Help! O2 sensor stripped and seized
Thread Starter
Race Car
Joined: Nov 2009
Posts: 3,526
Likes: 17
From: Ottawa
Heat, wrench, heat, wrench.... to a point where the wrenches could no longer grip the sensor due to so much material wear! Learned a lot though and had fun working on it. Could have used a bigger torch. 
I figure even if I micaculously am able to keep going and get this out, the threads are going to be absolutely destroyed and I won't get the new sensor in. So I decided that I'm ordering the M&K cat bypass pipe (and gaskets) and getting a local Porsche expert to install it for me. My new O2 sensor should screw nicely into that!
So since there was a hole where the ceramic portion of the sensor used to be, I used some JB weld and a washer to create a stop, and then an upside-down cap screw to plug the washer hole. Covered it in JB weld and it should cure overnight to plug that hole until I can get the new pipe in!
Pics, for fun:
.... I might have gone overkill on the JB weld....
I figure even if I micaculously am able to keep going and get this out, the threads are going to be absolutely destroyed and I won't get the new sensor in. So I decided that I'm ordering the M&K cat bypass pipe (and gaskets) and getting a local Porsche expert to install it for me. My new O2 sensor should screw nicely into that!
So since there was a hole where the ceramic portion of the sensor used to be, I used some JB weld and a washer to create a stop, and then an upside-down cap screw to plug the washer hole. Covered it in JB weld and it should cure overnight to plug that hole until I can get the new pipe in!
Pics, for fun:
.... I might have gone overkill on the JB weld....
Thread Starter
Race Car
Joined: Nov 2009
Posts: 3,526
Likes: 17
From: Ottawa
You don't think the threads would have been destroyed by the time it came out?
Yes, a real torch would have helped.... but I made do with what I had.
Any opinions on the M&K cat bypass? I like it because the O2 sensor bung is after the collector, unlike many other aftermarket units. I PM'd caferacer as I know he was looking to get rid of his - haven't heard a response yet.
Yes, a real torch would have helped.... but I made do with what I had.
Any opinions on the M&K cat bypass? I like it because the O2 sensor bung is after the collector, unlike many other aftermarket units. I PM'd caferacer as I know he was looking to get rid of his - haven't heard a response yet.
I haddah Google dat
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From: Fresno, CA
Mapp gas is better but you need to be careful not to get carried away.
Edit: One last resort would be to get the cat out, and put it on it's side, then cut the old bung out as cleanly as possible, like with a cutoff wheel on an angle grinder. Then you can weld in a new bung and install a fresh O2 sensor. I would not try to run for an extended period of time without the O2 sensor.
Edit: One last resort would be to get the cat out, and put it on it's side, then cut the old bung out as cleanly as possible, like with a cutoff wheel on an angle grinder. Then you can weld in a new bung and install a fresh O2 sensor. I would not try to run for an extended period of time without the O2 sensor.
Last edited by rusnak; May 30, 2012 at 12:31 AM.
Thread Starter
Race Car
Joined: Nov 2009
Posts: 3,526
Likes: 17
From: Ottawa
Mapp gas is better but you need to be careful not to get carried away.
Edit: One last resort would be to get the cat out, and put it on it's side, then cut the old bung out as cleanly as possible, like with a cutoff wheel on an angle grinder. Then you can weld in a new bung and install a fresh O2 sensor. I would not try to run for an extended period of time without the O2 sensor.
Edit: One last resort would be to get the cat out, and put it on it's side, then cut the old bung out as cleanly as possible, like with a cutoff wheel on an angle grinder. Then you can weld in a new bung and install a fresh O2 sensor. I would not try to run for an extended period of time without the O2 sensor.
Team Owner
Joined: Aug 2005
Posts: 28,418
Likes: 1,611
From: Cambridge Ontario Canada
the cat for starters .. if you care that is .. when you run rich the cat will have to work hard as unburnt fuel may be being dumped in . it will get super hot ...
fuel economy would sufer also i imagine
fuel economy would sufer also i imagine
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I haddah Google dat
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Joined: Nov 2008
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From: Fresno, CA
The reality was posted by Ingo (Ischmitz) over on Pelican. He has spent years and years going through the dme chips, and understanding the circuitry on the dme board. He rebuilds them, tests them, and I know very few people who have more knowledge AND are WILLING TO SHARE IT.
He explained that the 3.2 911 early Motronic does not have a routine that checks to make sure the O2 sensor is plugged in. If it's not present, the dme does not know this and sends erroneous pulses to the injectors, based on a false reading from the O2 sensor wires. Stray voltage and no voltage can make the dme operate rich, or lean. You are sort of at the mercy of the dme's ability to swing the mixture either direction, and whatever stray voltage is nearby.
Thread Starter
Race Car
Joined: Nov 2009
Posts: 3,526
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From: Ottawa
Not fun.... The new pipe will be here ASAP but I have to wait for the gaskets and hardware.
Maybe I keep working at removal in the meantime.... Damnit I hate when shipping holds me up.
Maybe I keep working at removal in the meantime.... Damnit I hate when shipping holds me up.
Thread Starter
Race Car
Joined: Nov 2009
Posts: 3,526
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From: Ottawa
For the longest time, years actually, I thought the same thing. I've read that there is a default map that the dme will read from, and that would make the dme run a rich setting for safety.
The reality was posted by Ingo (Ischmitz) over on Pelican. He has spent years and years going through the dme chips, and understanding the circuitry on the dme board. He rebuilds them, tests them, and I know very few people who have more knowledge AND are WILLING TO SHARE IT.
He explained that the 3.2 911 early Motronic does not have a routine that checks to make sure the O2 sensor is plugged in. If it's not present, the dme does not know this and sends erroneous pulses to the injectors, based on a false reading from the O2 sensor wires. Stray voltage and no voltage can make the dme operate rich, or lean. You are sort of at the mercy of the dme's ability to swing the mixture either direction, and whatever stray voltage is nearby.
The reality was posted by Ingo (Ischmitz) over on Pelican. He has spent years and years going through the dme chips, and understanding the circuitry on the dme board. He rebuilds them, tests them, and I know very few people who have more knowledge AND are WILLING TO SHARE IT.
He explained that the 3.2 911 early Motronic does not have a routine that checks to make sure the O2 sensor is plugged in. If it's not present, the dme does not know this and sends erroneous pulses to the injectors, based on a false reading from the O2 sensor wires. Stray voltage and no voltage can make the dme operate rich, or lean. You are sort of at the mercy of the dme's ability to swing the mixture either direction, and whatever stray voltage is nearby.
If its only sending random signals to the injectors I feel te engine can probably deal with rich or lean settings for the short term. I'm guessing a faulty O2 sensor would yield the same results as the signal would be incorrect (unless a bad O2 sensor sends a constant "bad" signal that tells the DME to run a certain way).
If it sends erroneous signals to the spark plugs that's another issue.... I could see pre-detonation being a potential problem.. EDIT: this doesn't make sense, the O2 sensor readings should have zero effect on spark timing.
Team Owner
Joined: Aug 2005
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From: Cambridge Ontario Canada
yes Jonathan keep working at it .. if it is moving just spray and work back and forth .. it will come out .. once you remove the cat from the car it will be allmost impossible to remove as you have no way to hold it steady .. so get back under there and get wrenching..
Thread Starter
Race Car
Joined: Nov 2009
Posts: 3,526
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From: Ottawa
yes Jonathan keep working at it .. if it is moving just spray and work back and forth .. it will come out .. once you remove the cat from the car it will be allmost impossible to remove as you have no way to hold it steady .. so get back under there and get wrenching..
It moves about 1/5 rotation every half hour. Hopefully this rate increases tonight with round 3!?
Any other recommendations for gripping it? Even the pipe wrench is slipping now that it's become so rounded off. I really need to weld something to it....
Team Owner
Joined: Aug 2005
Posts: 28,418
Likes: 1,611
From: Cambridge Ontario Canada
if its moviing now can you get the big *** vice grips back on it ? the disadvantage of a pipe wrench is you can only go one way without reconfiguring ,.
i would put the vice grips back on and just work it back and forth in one spot for abut 10 minutes, then you should slowly begin to increase how much your back and forth motion will cover and keep spraying . remember all the threads move when you do this and it will loosen up . then you can remove it ..
and having a working cat on the shelf with an O2 sensor in it is never a bad thing ..
Btw which bypass did you get ?
i would put the vice grips back on and just work it back and forth in one spot for abut 10 minutes, then you should slowly begin to increase how much your back and forth motion will cover and keep spraying . remember all the threads move when you do this and it will loosen up . then you can remove it ..
and having a working cat on the shelf with an O2 sensor in it is never a bad thing ..
Btw which bypass did you get ?
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From: Middle GA.
Been reading this thread,..(cringing),..feeling a bit guilty at my recent successful endeavors on my O2 sensor changeout on my '89. For some weird reason, the service history documents never showed this part as being replaced (hard to believe, actually).So, I decided that it was time.
2 days prior, I soaked that puppy with Kroil X3 times...come time to do the deed, she came off with ease,..making use of an open-ended wrench,..the sensor had plenty of anti-seize on it, surely a graceful gesture from the person who was in there last. Hell,..even the grommet went in without too much fuss.
"Rubbing it in" aside,...
You may consider getting it to a muffler shop. Those guys can make it happen real quick.....sure sounds like you're right about the need to tack weld something to it....
Sorry to hear of this trial,...WOW,...I (vicariously) feel your pain.......soon, the triumph will come,..and it will be a great story!
Best!
Doyle
2 days prior, I soaked that puppy with Kroil X3 times...come time to do the deed, she came off with ease,..making use of an open-ended wrench,..the sensor had plenty of anti-seize on it, surely a graceful gesture from the person who was in there last. Hell,..even the grommet went in without too much fuss.
"Rubbing it in" aside,...
You may consider getting it to a muffler shop. Those guys can make it happen real quick.....sure sounds like you're right about the need to tack weld something to it....
Sorry to hear of this trial,...WOW,...I (vicariously) feel your pain.......soon, the triumph will come,..and it will be a great story!
Best!
Doyle