Oxygen Sensor Removal Notes

Became a member of the club over the weekend. Took about 4 hours and I have a 4 post lift in my garage which helps. This is for a 1991 NSX and I purchased the Science of Speed O2 sensors.

To get to the rear sensor I removed the shielding on the exhaust and manifold to get more room. Also removed a transmission/suspension brace to get extra clearance. Did the usual soaking with PB Blaster and heat. A 7/8 O2 socket wrench would not work as it was too tall to get a 3/8" bar on. The offset O2 socket just opened up and I was worried about rounding the nut of the O2 sensor. I finally cut down the connector (part that clips to chassie - but did not want to destroy in case I was unsuccessful in getting sensor out) and slid a 22mm closed end wrench over it. Before I did this I heated the bung with a propane torch for about 7 - 10 minutes. Put the socket over and managed to get a cheater bar over one of the open ends of the other side of the wrench. Bang - finally let loose.

The front one was not as bad. Did not seem to have as much corrosion. Was a little tuff removing the manifold shielding but despite some nicked up hands was not that bad. You need to remove the shielding to get close to the O2 sensor nut. Again lots of penetrating oil and finally heat. I slid the open end of the 22mm wrench on the O2 sensor bolt, put the closed end in a large diameter cheater bar, made sure I was spot on and pulling in the right direction and came right off. The tall O2 sensor socket was again too tall and the offset one just opened up.

I read several accounts of how people have done this and they all seem to be different. The most important thing was to get enough heat into the manifold with the propane tourch. If I were to do this again I would heat for over 10 minutes as I think this helped the most.

Good luck,

Drew Altemara

I changed bank 1 sensor 2 today, due to its heater element failing. Both primary sensors also failed that way, but were covered by the old extended warranty. In preparation, I sprayed this sensor with PBlaster and took a short ride.

It was easy to get at from the floor, not even requiring me to put the car on my lift. That ends the easy part. The O2 sensor socket with the slit to go over the wiring, as others have stated, was useless. It just flexed and rounded the nut on the sensor. This was the original sensor, so I cut off the "cup" around the sensor to get clear access to the sensor nut. That was another nasty job - very tight space to get a chisel or tiny grinding wheel into to cut off the "cup".

Once the "cup" was removed, I cut the wire off of the old sensor and use a 12 point box wrench. The sensor came out effortlessly, I didn't even use the full 1 foot length of the wrench for leverage. This once again proves the slit O2 sensor removal sockets are worthless.

Out of curiosity, that "cup" around the sensor didn't come with the new sensor. (I went for Walker since I've not had any other car lose so many O2 sensors especially at only 80kmi and therefore won't buy Denso.) Does that cup do anything but make removal difficult?

Which brand sensor / part numbers are you guys using? What year cars?

(I went for Walker since I've not had any other car lose so many O2 sensors especially at only 80kmi and therefore won't buy Denso. '96 NSX-T, red/tan) For bank 1 / sensor 2 I used the Walker 250-24121, which fit perfectly, including the rubber grommets around the cable that snap into brackets that keep the cable away from the exhaust system. From RockAuto, it was all of $37.78 including shipping. Note that NSX mechanic extraordinaire Larry Bastanza regularly uses Walker 02 sensors.

In the past year, the SLK lost both secondary sensors (OEM Bosch). I replaced one with Walker and one with NTK (the company that makes NGK spark slugs) to see which last longer. I have much more confidence in NTK than Denso, based on the original failures of the primary units in my NSX, covered by the 14 year warranty the EPA forced on Honda/Acura for some no-no's from '95 - '97.

If you haven't looked at RockAuto, try them (http://www.rockauto.com/) . They have a wide range of parts at excellent prices, with quick shipping. They also are presently having a sale on some NSX parts they are ceasing to carry because of lack of demand. I picked up a few coil packs that way. Just remember that from most parts catalogs perspective bank 1 = rear bank (with cyl #1 ) when trying to determine which sensor to order..

I had to remove both of mine. The front one came right out but the rear one was stuck. I sprayed it with WD40 a few times over the course of a day and let it sit until the next day. The O2 socket worked for me that I purchased from oreily, it weighs a little over 1/2 lb. Didn't notice any flex, I just put the socket on and smacked the ratchet handle with a small hammer and it came loose. If your having trouble getting to it, not that hard to unplug the sensor and remove the CAT. Then you can work on it on the bench.

ftuhy
I don't know what cup you are talking about, maybe mine doesn't have them?

Mike

Try this next time. I use it daily on hvacr and no longer do I need fan blade pullers after using this stuff. This makes wd40 laughable it works so damn well. My exhaust bolts popped right off after 1 minute using it.
http://www.clenair.com/products/penetrate-hd

May be a little late now; but, for those who are doing future replacements, AC Delco (part # 5613695) and Bosch make a thread lubricant / anti seize for O2 sensors. It greatly facilitates future removal. The Delco stuff is available, I have never been able to find the Bosch product. Apply to the threads and definitely keep it away from the sensor holes.

Don't get any silicon type sealants near your o2 sensor. Silicon is death to the sensor element.

Some new sensors are supposed to come with a grease pack for the threads and I have seen claims that the Bosch sensors come pre greased. However, none of the Bosch LSU series widebands that I have installed had a grease pack or any kind of lubricant / anti seize on the threads (that I could see or that would come off when wiped with a cloth)

The NTK and Walker sensors that I've ordered in the last year all came with a tiny tube of the lubricant.

Mike,


Here's shots of the secondary sensors. The one with the "cup" on it is the factory installed original. The one without the cup is the replacement. The second picture is a close-up of just the one with the cup.

Its tough to get the washer off a sensor once it had torqued down, and then removed. The cup goes between the sensor and the washer. Perhaps the $250 extra for buying the sensor from Acura is for the cost of the replacement cup However, since I wouldn't pay that price, I have no idea if the cup indeed comes with the sensor from Acura or if its a purchasable separate part.

I seem to vaguely recall those being on the secondary O2 sensors on my car. The parts diagram doesn't list them as a separate part and the parts diagram makes it look like they are part of the replacement secondary sensor. It doesn't look like they are on the primary sensors.

I suspect that the 'cup' is intended to be a splash shield for the secondary sensor. The O2 sensor body runs quite hot (stink'n hot) and the sensor elements take poorly to thermal shocks, so the shield might be there to prevent water spray from hitting the sensor body. That would be less of an issue for the primary sensors. The shield might also be a thermal shield to help the sensor stay hot; but, I am less inclined to believe that.

Don't drive in the rain and stay out of puddles (listen to your mom :smile and the lack of the cup probably won't be a problem.