New oxygen sensor + installation, need help

[Cruisin'Carolina]

If I had to do it over again (94, cats side by side) I'd probably just pay to have it done. Rust free truck, those bolt-outs were a lifesaver.

And heed the advice of getting the ratchet box-end wrenches. I should have. I elected to drop the tubes, and ran into other difficulties/frozen bolts/heat shield fabrication stuff.

Killed an entire weekend.

 

[derrickbwg]

I had the front sensor go out on me and the nuts were as rusty and corroded as I've ever seen. Put off the change for a while because they were in such bad shape and difficult to remove.

During that very long time of running with the bad sensor I started doing the numbers for mpg and was astonished to find it hitting 16.5-16.7mpg consistently (many,many tanks) on the long trips and even doing 15 around town. Before the sensor went out the truck was a lousy 14.3?!?!?!? A truck I had always complained about in regards to efficency had turned into a truck I was bragging about to the wife

Doesn't the reading go to a factory default setting if the sensor goes bad? What would be the reason for the increased mileage under the bad sensor and decrease in my mpg's after I fixed it? I know nothing about these or the electronics but I did the calculations enough to be sure I've lost 2mpg...lol

I'm keeping the old sensor in case gas goes throught the roof

sorry for the hijack......back to topic....I made sure to put anti seize on this installation.....I had to resort to a pair of locking pliers to grab hold of the once flat surfaces and took about an hr.

 

[landcruising]

I have not recieved the nut splitter yet and am considering the Dremmel. I expect it to be a pain laying on my back, so I may just pay the $ to have them removed, just trying to save the $ for the $4K in upgrades remaining

 

[Sc0-]

My mileage dropped as well after replacing the sensors but the power improved...

BTW: as a WARNING to those people with ratcheting wrenches that don't reverse be careful with them and make sure you have room to remove the wrench after you start tightening/loosening something. Could be a cause of a LOT of stress and something broken!

 

[bpenn1980]

Just got done replacing both sensors on my '94. Relatively painless, took about 4-4.5 hours with some wasted time in there. I sprayed my sensors with wd-40 24 hours before hand and that may have helped. Also, buy the flexible wrenches mentioned previously in this thread...very useful. I'm a big guy and have big hands and I was able to do this. Here's a little step by step covering what I did (except the useless stuff I wouldnt repeat)

1) Gather 12mm socket, ratchet (I used a stubby and normal), ratchet extension (3"-ish), 12mm flexible ratcheting head wrench, 10mm and 12mm Craftsman bolt-out in case yours are rounded off, normal size flat head screwdriver, very small flat head screw driver and anti-seize.

2) Slide in head first with headlamp on and reach up around the exhaust pipes and get the flex head wrench on the No.2 (inner) sensor bolts and hopefully they'll come off. Its a little awkward positioning, but it works. You can see these pretty easily from this position. Use small flat head screwdriver to hold molex connector open and work connection apart. Finish removing No.2 O2 sensor. Install new sensor and bolts, making sure to use anti-seize on studs. Plug new sensor back in.

If there are problems getting these bolts off you should have plenty of room to use the bolt-out socket.

3. Slide around so your feet are sticking out past
the PS front wheel. Next to the catalytic converter there is a heat shield held on by two bolts. Remove these using the flexible wrench. Looking toward your feet you should be able to see the No.1 (outer) sensor pretty easily. I had to use my bolt-out socket on one of these because it was slightly rounded off. There is enough room to use a ratchet...barely. Unplug sensor using the same technique, or whatever works for you, but my fingers still hurt from the ultimately unsuccessful pressing and pulling technique. I will use the screwdriver from here on out. My connector was secured behind the wheel well with two zip ties. I would recommend using two new zip ties after the new sensor is installed. Install new sensor making sure to reinstall the sensor's heat shield and use anti-seize on studs. Plug sensor in and zip tie in place.

3) Replace heat shield for catalytic converter.


I believe thats it. It took me an extra hour or two because I was attempting to remove the heat shields from the exhaust pipes. I got it in my head that this would be helpful. Maybe it would have been, but I ended up abandoning this and just doing the sensors with the shields in place...but not after a got halfway through cutting a bolt off with a dremel tool I'm going to need to address that at some point with a new nut/bolt and clamp.

Pretty straight forward. I used protective eye glasses and a small LED headlamp which were helpful. I have a bunch of dry dirt under there that was falling in my eyes and the headlamp is useful for the obvious reason of being able to see

[EDIT: Replacing the O2 sensors stopped my high idle on start up. EDIT TO THE EDIT: Not true. Only stopped the high idle on the next start. Now back to high idle. EDIT TO THE EDITED EDIT: Cleaned throttle body, IAC, MAF and replaced PCV which has stopped my high idle on start up and low warm idle. ]

Hope this is helpful to some out there!


Pictures of old sensors:
O2 Sensor Replacement - a photoset on Flickr

 

[landcruising]

O2 sensor update

I could not remove a bolt on the rear O2 after trying bolt outs, a nut splitter (which broke), and then attempting to get access with a dremmel. I decided to take Romer's advice and took it to a shop to remove with new O2 in hand. They quoted me an hour labor at $93 including tazx etc. so I accepted. About 3 hours later I get a call, the stud broke so they attempted to tap it. The tap broke in the stud hole. So they now suggest a larger tap and replacing with a slightly larger bolt and nut. Now a $183 bolt removal. It is now 4:00 and they cannot finish today. So hopefully they can get fixed tomorrow. I hope I am not looking at a new exaust or over to a shop to weld a new plate etc. This is by far the most effort I have ever had dealing with a nut removal in my life.

This mechanic was well recommeded by my jobs fleet mechanic who didn't have time to help me with my delima. This mechanic stated that the rear O2 sensor (behind the cats on a 97) rarely goes bad and usually sends a code for CEL if the cats are bad and does not control the fuel or ??. It passed CA smog 3 month ago when I bought it after 2 trys (as shown on the states website) but had a recommnedation to replace the O2 sensors because of week signal and a CEL code. It was the original O2 with 107K on it and was a SO Cal cruiser its whole life but was close to the beach. It appears very rust free with the exception of the exhaust and a few other aluminum pieces which are rusted or pitted including the wheels. So the mechanic beleives that I may need to replace the exaust at $400++++ if he cannot get the tap to work and it still throws a CEL code.

1. Does the rear O2 CEL code mean a cat is bad or could the O2 just be bad and sending the wrong signal?

2.What is the purpose of the rear O2 sensor?

3. What is an expected cost of a new exaust system with Cats.

Any experience with this out there is appreciated?

 

[archie]

I would have clamped the broken stud portion down with a hose clamp (or similar) and bolted on the other good stud. You could have saved that $183 for the new exhaust you need eventually down in the future.

 

[LandStalker]

I just replaced both Heated Oxygen Sensors on my '94 yesterday. PITA!!!

No rust on my LC, but the nuts on the outside sensor were really bad. Sprayed with PB 7 days before and the morning of starting all the work. Tried to use Bolt-Outs, but they didn't work for this. Not enough clearance to hammer the BO down onto the nut. Tried using a Dremmel, but it was taking too long & it was difficult not to hit the stud threads. What worked for me was the high-tech tandem of a hammer & chisel.

The inside sensor was much easier since the nuts were still in good shape. After both sensors were off, I replace the inside, then the outside.

After everything was back together, I noticed that there was a bracket after the cats that was not bolted to the exhaust line. The bracket has 2 bolt holes and hangs down underneath the exhaust line. There was about a 1" gap between this bracket and the line. I'm sure that if this was bolted correctly, it would force the line down away from the body. This would've added another 1/2" of precious clearance above the sensors. Just something to check before you start.

Today I pulled the EFI fuse for 60 seconds and cleared the Check Engine Light. After about 2 minutes of driving, the CEL popped back on. Used the "paperclip" trick and got code 28. WTF??!!!!
Now I need to find out which sensor is #2, Inside or Outside? What else could be causing the code 28? My LC is creeping up on 170k.

 

[bpenn1980]

I just replaced both Heated Oxygen Sensors on my '94 yesterday. PITA!!!

No rust on my LC, but the nuts on the outside sensor were really bad. Sprayed with PB 7 days before and the morning of starting all the work. Tried to use Bolt-Outs, but they didn't work for this. Not enough clearance to hammer the BO down onto the nut. Tried using a Dremmel, but it was taking too long & it was difficult not to hit the stud threads. What worked for me was the high-tech tandem of a hammer & chisel.

The inside sensor was much easier since the nuts were still in good shape. After both sensors were off, I replace the inside, then the outside.

After everything was back together, I noticed that there was a bracket after the cats that was not bolted to the exhaust line. The bracket has 2 bolt holes and hangs down underneath the exhaust line. There was about a 1" gap between this bracket and the line. I'm sure that if this was bolted correctly, it would force the line down away from the body. This would've added another 1/2" of precious clearance above the sensors. Just something to check before you start.

Today I pulled the EFI fuse for 60 seconds and cleared the Check Engine Light. After about 2 minutes of driving, the CEL popped back on. Used the "paperclip" trick and got code 28. WTF??!!!!
Now I need to find out which sensor is #2, Inside or Outside? What else could be causing the code 28? My LC is creeping up on 170k.

Outside

 

[blu 60]

Well, I just did this last week on my '94, which should be indentical to your truck. Admittedly, I have a lot of tools, and my truck is from dry country (another time it pays to buy a vehicle from dry country!), but it only took me about 45 min. PB Blaster is your friend here. I sprayed some on the nuts about an hour before I started. If your truck is not from dry country, spray that on a day ahead of time. Be generous.

I used a Gearwrench flex combination wrench (WRENCHES > Ratcheting > Flex Combination > | GearWrench™)
to take that outer heatshield off. This is the shield closest to the running board. There are two bolts that hold it on and with that wrench it comes off in about a minute. Use a 1/4" drive small ratchet and a 12mm socket to loosen the two nuts on that outter sensor. A ratchet with fine teeth is the best way to go; course teeth are pretty worthless on a 1/4" drive. I think Sears finally started making some good ratchets again and they might have one. They should have that Gearwrench set too, or your Lowe's or maybe Home Depot will have it. Anyhow, remove the nuts, pull little heat shield and the sensor, disconnect the lead and remove. You'll be glad you have parts from CDan and the new one goes in perfect with a new gasket, some anti-seize, new nuts, connect the lead, and snap the hold-down in the hole Mr. T put in the sheet metal for just such an occasion. Put the two bolts in that held the heat shield on. Sensor one done in about twenty minutes on a bad day.

Go to the next side, use same technique, but no heat shields to deal with. Bob's your uncle. Done.

This is a job where the proper tools make all the difference. Don't waste time, get the right tools, you'll use them again. You'll need that Gearwrench set when you want to take that upper hold-down bolt off the tube at the top of the PHH (Pesky Heater Hose) when you realize you need to do that too, if you haven't already. A good 1/4" drive metric ratchet set in invaluable. I'll say it again, fine-toothed ratchet.

If your fittings are rusted beyond recognition, I don't know what to tell you.

Keep the Cruiser Faith !

Hey

I followed super90's instructions 20 minutes and the tools were put away.

Many thanks for the tip!

 

[LandStalker]

Outside

Thanks bpenn. Don't know where i would have found that one. Doesn't specify anywhere in the TFM.

Sunday I broke out the resistance meter and tested both the inside and outside sensors. Both read about 11-12 ohms on a cold day, so i guessed that looked about right. After pluging & unpluging the outide sensor connector a few times, I popped the ECM fuse out to reset the memory. Then started it up and let it idle for about 10 minutes. I reved up to 2500 rpm for about a minute, then drove around for about 45 min more...
The CEL never came back on! I now have a perfectly running 1FZ-FE in the 'Stalker! Gonna have to go for a long drive now to see if the MPG's increase at all.

 

[deputy630]

Ok Fellas did the 02s on my 94 LC. First put PB on there about 3 days in advance. Then before I started I gave it another shot. They came off no problem at all. I didnt have to remove the heat shields just got in there and got her done. It has been the easiest thing so far to do took me all of about an hour. I would like to thank everyone who typed in to give advice on this topic. Didnt think I could do it until I read the post...... Thanks Danny

 

[sdbrassfield]

OEM Denso sensors from oxygensensors.com were 170$ shipped for my rig. They (connectors/wiring) plug right in and are a direct replacement. They come with the gaskets. Check your bolt studs on the flanges also. They can be a b*tch if they are rusty. If they are rusty, pbblaster and new nuts may be in order also.

 

[vt92]

1. Does the rear O2 CEL code mean a cat is bad or could the O2 just be bad and sending the wrong signal?

2.What is the purpose of the rear O2 sensor?

3. What is an expected cost of a new exaust system with Cats.

Any experience with this out there is appreciated?

2. The rear O2 sensor verifies that the cat is working and helps tweak the air/fuel adjustments that the front one is doing.

 

[nicholas]

I changed out both O2 sensors on my 97 today. The front sensor had already had the OEM nuts replaced with some stout 13mm nuts which made the removal a breeze. The hard part was scraping the old OEM gasket of the bung. It took at least an hour and I believe a small chunk of the rust actually fell into the pipe near the opening of Cat #1. Hopefully this won't significantly effect the cats.

Here are a few things did that made it somewhat easy:
1. unbolted the lower front PS running board bracket bolts and the lower of the two upper bolts. I left the top bolt in and just loosened it so I could swing the bracket back to get better access to clean off the old gasket rust.

2. I actually had to pry off two of the forward spot welds that hold the rear sensor shield in place (the one that bolts on to the actual sensor studs) so I could gain better access to the rusted beyond recognition OEM cone nuts on the rear sensor. I had treated the nuts with PB blaster on two occasions prior to this. I bought some nut removal sockets (similar to the bolt outs pictured previously in this thread) from harbor freight ($16 well spent). The set came with a about 6 or 8 different metric sizes. I used a 10mm to remove the nut closest to the ground and an 11mm to remove the one closest to the body. Those nut removers are a lifesaver! I too was contemplating replacing the bung with Cristo's bung because I couldn't get enough room to pound the sockets onto the nuts. I ended up reaching over the output shaft before the rear drive line with my right hand and pounding the nut remover's on while guiding with my left. I couldn't believe how smoothly those things worked.

3. Used the recommended anti-seize compound which will hopefully help with the future removals.

A word to any newbies trying to save a buck.....before I found this forum I let my roommate (who had successfully used a bosch O2 sensor on his H*nda) talk me into using a generic bosch O2 replacement. What a joke. The damn thing never worked and my CEL stayed on even after removing the codes. The exhaust smelled horrible too. A complete waste of 50$. I have repented and now only buy OEM parts from the great parts Shamen (CDan). The CDan O2 sensors are working well and my exhaust smells good enough to breath. For your own sanity and your pocket book in the long term, only use Toyota OEM parts!

Thanks to everyone that contributed to this thread. The bolt-outs are amazing!

 

[Riley]

I just changed mine today, I second the bolt-outs, they are amazing.

The only trouble I had was getting one of the frozen nuts off my sliders (needed to gain access).

really the entire tune-up was a 1 or 2 banana job if you overlook my slider hassles.

 

[Altaf]

Any O2 sensor nuts out there that won't rust? Granted I may not even have the Cruiser the next time the O2 sensors need to be replaced but the next owner may appreciate it...

 

[80t0ylc]

Resurrected this thread for 2 reasons.

1. I didn't think it necessary to start a new thread on this subject and

2. Seems to be a few folks, besides myself, replacing O2 sensors lately.

It took me a couple hours because I didn't remove anything like heat shields or USPS slider/running board. I didn't use any special tools, they probably would have cut some time off. Also gave the nuts some Liquid Wrench and started it up and drove it into the garage which just slightly warmed it up and provided some vibration to help 15 minutes before tackling the nuts. Used a 12 mm 1/4 drive socket/ratchet on 3 out of 4 of them. Last 1 - front nut on inboard sensor had clearance problems, so a 12 mm box end wrench worked. All 4 studs were still in good shape. The 2 outboard nuts were starting to get a layer of oxidation, but the trusty box end s****ed it off so I could get the 6 point socket on. I also used a 3/4 extension for a cheater to get more leverage on the ratchet handle to break the nuts loose. Inboard nuts were much harder to get to, but in better shape, thank God!

Also, pulling ECU fuses did not reset the CEL or ECU. It required pulling a battery cable. Damn CEL's been on for 2 years, I think it needs a rest.

I highly recommend going OEM through c-dan. Price was $226.33 shipped to my door and included new nuts and gaskets. I'm hoping to get another 200K+ out of these. Here's pics of old and new:

 

[Rich11]

Do the autozone type auto parts stores carry the replacement bolts and gaskets? I'm planning on changing my o2 sensors on my lx450. I ordered the o2's but prolly going to need new bolts as mine are rusty like everyone's else...

 

[96Cruiser]

Do the autozone type auto parts stores carry the replacement bolts and gaskets? I'm planning on changing my o2 sensors on my lx450. I ordered the o2's but prolly going to need new bolts as mine are rusty like everyone's else...

not sure on the gaskets from autozone, but I went with denso sensors from the net,[they came with gaskets] supposedly same as oem, and for the replacement nuts, I had previously installed oem nuts on the rear of my borla and the front when I replaced the y-pipe. Both were rusted badly the rear since 2006 when I installed the borla and I had to dremel them down to a shell and use some pliers to finally get them off, the studs were rusted as well but there was enough threads to reinstall the new sensor, the front had froze on the new y-pipes studs and the first one came off however the second one snapped the stud, forcing me to remove the 1yr and 10 month old y-pipe, luckily advance warranted it for me.

I sourced copper manifold nuts 8mm x 1.25 [found a listing on ebay, but needed them the next day] they were a bmw part number[18 30 7 620 549] and a trip to the local bmw dealer netted me the 2 pair I needed, hopefully these will last. a trip to the local boat supply got me stainless steel bolts and washers for the converter flanges, but I used matching brass nuts from NAPA with those, cause all the factory stuff was junked[new when the y-pipe went on 1yr and 10 months ago]

hope this helps

doug