O2 sensors, the root of ( much ) evil........

Cossack · Post by **Cossack** » 16 Aug 2004, 21:57

Hi!

I use this site a lot to troubleshoot and fix my Volvo with great success, so I thought I would contribute to it with a recent story.

My '94 850 Turbo was very sluggish on acceleration, especially from stop, all the way to ~2500 rpms and then it would suddenly kick in. This would also happen on the highway at high speed, with the car not accelerating consistently with the amount of gas given. Th idling also got progressively worse, surging quite a bit.

I thought of many things - tranny, engine problems...... I had codes pulled up and bot the front and rear O2 sensors came up.

Dealer wanted 825$ Can for the job, so I looked at doing the job myself. Trust me it is a very easy job if the instructions on this site and Bay 13 are followed. The sensors can be found ar Carquest or any other generic parts supplier. The Bosch universal does a fine job and is VERY EASY to splice in (instructions come with sensor) at a fraction of the cost. Total price should be below 100$ US for the front sensor, see http://www.oxygensensors.com

I suggest replacing only the front one even if both codes are coming up (front and rear O2 sensor). the front one is the most critical to adjust the fuel mixture, and you'll find that there are fewer options for replacement of the back one out there, perhaps indicating that it is not as critical.

I personally replaced the front one only and neither computer code has come back up, and the car is running like new!!!!

Good luck and keep an eye on those O2 sensors, they can make the car feel almost unusable if they go!!

Post by **matthew1** » 16 Aug 2004, 22:57

Thanks for that O2 sensor success story Cossack!

I'd like to add that when you're all done, there's no need to reset the codes because the system will determine if the fix truly fixes the problem, and extinguish the light in a few dozen miles if it does.

lek · Post by **lek** » 20 Aug 2004, 22:35

I just had my O2 sensors replaced at the dealer. VERY $$$$! I was 1 hour into a 5 hour drive back from vacation when the check engine light lit. This had happened once before & I had called service from the road. This time I was not too worried because I had been told that the car was probably just sensing that emissions too high, but that driving & safety would not be affected. However, I started to wonder if the car was ok. Every once in a while, the car seemed to vibrate, as if the road surface was textured. In fact, at first I really thought that this was the case, because sometimes the vibration would stop when the road surface changed. But after it returned several times, I began to get nervous. I could feel the vibration in the steering wheel. Then it would be fine for a stretch, only to return as I began to relax. I took the car to the dealership (I know, I know). They told me I needed to replace the oxygen sensors, but that they were unable to duplicate what I had described & that no other codes came up. The shakes are not gone. Only happens highway driving. I've tried to figure out if it starts at a particular speed, but this does not seem to be a factor. Could this be related to the O2's? Any ideas/ suggestions? Thanks

alanb · Post by **alanb** » 21 Aug 2004, 07:40

I got the socket and tried an oil penetrant and the sensosr still won't come loose. Any suggestions on how to loosen this thing?

Post by **matthew1** » 21 Aug 2004, 17:26

Try an open-end wrench with a cheater bar. My front sensor was pretty reluctant to unscrew.

As for the poster with vibrations, I'd be very hesitant to ascribe vibrations to an O2 sensor or anything to do with emissions for that matter. I'd look at trans fluid level/color/smell, engine mount condition and have my wheels balanced.

Guest · Post by **Guest** » 27 Aug 2004, 10:10

I think the rear o2 sensor is for emission control(the post cat o2 sensor), if that comes up on your smog test you`ll fail... which wouldnt look good on your carfax.

Tom