O2 sensors on 3FE really hard to replace?

[Matmal]

check engine lights on with o2 code, they are way past due and I already have both replacement sensors. My dad told me a local shop said it'll cost around 140 to replace them and there is some rust on some parts that may break and increase the bill.

I got the FSM, but can only find o2 diagnostics not replacement. I have done a ton of work on my own car including o2 sensor and it was super easy.

So, how much junk needs to be removed to get to these suckers? I am a DIYer so I'd love to save him money and do it myself but dont want to break something, or be out there all day Fing with it. thanks for any tips.

 

[Matmal]

Oh also I have searched but didnt find any info on doing the 3fe sensors.

 

[Alleycats]

O2 sensors (2) are just before the catalytic converter, crawl underneath and have a look. Shouldn't be too difficult although sometimes the nuts are apparently rusty thus requiring vice grips.

 

[CJF]

Can range from super simple to PITA depending on rust issues and quantity/quality of tools.

Hit all the nuts with some liquid wrench for a few days in a row, then have at it.

 

[Matmal]

OK great, now when you say all nuts, you are talking about the nuts that hold the O2's in place, or are there other parts I need to take off to gain access?

If its just the O2 nuts, I'll definitely tackle it myself.

The shop my dad went to has always been good to us, and with this job they got all ready to do it then called him and said how much a PITA it looks like it will be and gave him a new price and then decided not to do it... as I recall it was an access issue with exhaust pipes needing to come off, but if that's BS I would love to get these in there and stop driving on bad O2s.

 

[Lka1988]

Two nuts hold each O2 sensor in place. Like Curtis said, hit them with a crapload of Liquid Wrench/PB Blaster/some sort of rust penetrant for a few days before even attempting to touch them.

Oh, BTW, don't bother with the cheap aftermarket O2's, you'll be replacing them next year. Get OEM, trust me. Call CruiserDan (does he still do stuff around here? it's been awhile...) for your parts.

 

[Matmal]

Thanks a bunch guys.

the O2's I have are denso... from searching I believe they are OEM... yes?

 

[Lka1988]

Yes, but they are not the same as a set of Denso's you can buy from the local parts house. Like I said, call CruiserDan (he's a member here) and order from him. He's located at a dealership in New Mexico. He will get you exactly what you need and I believe he gets you a discount as well, but don't quote me on that.

 

[BamaPaul]

Densos are what I have been running in mine for over 2 years now without issue. I bought them from rockauto.com for a decent price too

 

[Matmal]

So I wanted to ask about harm done to the truck from driving on shot O2's. The emission numbers all passed and were very good last summer except the fuel mixture was at the limit (unburnt HC and all else was very low). I know the cats can be hurt from it, i guess thats not the end of the world, but should I be concerned about anything else? the engine was rebuilt before we got it at about 170k, it has 200k now. thanks guys.

 

[Lka1988]

I wouldn't worry too much about it. The fact that it passed a sniffer test means that HC levels are in an acceptable range. Just get new O2's in there and you should be good.

 

[AK101]

One was 'easy' to access...the other is behind some crazy heatshield that is evidently hard to access w/o a lift from what I understand.. my 91 is rust free so the one came off super easy.

 

[Golgo13]

I think @jonheld has some good info on this. There was another post recently about the heat shield you speak of, but I can't remember the title. You might just need a ratcheting wrench like a gear wrench or similar to get the 2nd one off. I have found that except for rust, these trucks are really easy to work on. You says yours is "rust free" and I'm jealous. When I got my truck, the jack-wagon before me welded the O2 sensors to the exhaust. I replaced it with a system from EMS Powered and everything is good now.
Make sure you use high-temp anti-seize to make it easier next time.

Also, for anyone else reading, I have given up on PB Blaster and Liquid Wrench. I will only use WD40 Specialist Rust Penetrant now. That stuff is incredible. Give it a try!

 

[mthom916]

Yes definitely presoak all nuts in PB Blaster or some other penetrating oil. The 91 should also has rock or can guards which can be a pita. If they are not there you'll know why.

 

[Hornd]

I have found heating them with torch helps immensely. I heat then hit with PB blaster then put the torque to them.
Get the special sockets at Autozone for $20. They pay for themselves on first use.
Don't be afraid to heat, spray, torque several times before they come loose. Sometimes it take 3X before they come free.
It sure beats rounding them off.
Just don't heat the new one or you wasted your $ as they will be junk.

 

[Matmal]

I was thinking a socketing gear wrench, I just wish those autozone ones were 6 point not 12. I have stripped nuts with 12 points. The 6 points I've used have been amazing.

 

[pawnthatdude]

Sorry for the thread resurrection. Does anyone happen to know off hand what size the nuts are?

 

[Mark W]

12mm. But usually that probably does not matter. they are likely to be rusted lumps. If they are, a 12mm socket will just spin and slip, if it bites at all. If that is the case, run down to Lowes or Home Depot and buy a set of the "Irwin" (brand) nut removers. They are like an extractor for broken bolts but inside out. Sharp reverse cut flutes inside the socket to bite into severely rusted nuts. If you have an oxy/acetelyne torch heat the nuts to red hot and let them cool. A MAP torch will do it too. Then hit them with some Ed's Red (or other penetrating oil if you have to). Use the nut "extractors" and the will come right off. They might come off without the heat or even the oil. But you will not be hapopy if you snap the stud, so play it safe.

You *might* be able to hammer a smaller 11 point socket onto the rusted nut. But the nut removers are a great tool to have for the future and not expensive.

Mark...

 

[FJ80 Money Pit]

I just removed rusted rounded nuts caused by the previous owner, after presoaking with Kroil Oil using a 6 sided 12mm 3/8 socket with a pivoting head wrench and extension bar due to the space issues. Crack em then respray and turn the other way then loosen and tighten and loosen and tighten until the threads get lube on em. Then replace with 13mm nuts (harder to round out) and antiseize. You can clean them with MAF cleaner or throttle body cleaner that says its safe for O2 sensors. Why buy new if you dont have to, we got old trucks so lets keep em that way!