oxygen sensor

Hi- I own a 2000 pontiac grand prix gt- 3.8 engine. Recently, my gas mileage dropped considerably (12mpg) and I am thinking of changing the oxygen sensor. The "check engine " lite has not come on yet and I was thinking of getting a scope test done , but at the price of the new sensor ($20.00) why spend $50.00 on getting it tested first-just change it. But on my car, there are 2 sensors- one up front and the other after the converter. Do I really need to change them both, or just the front one? Thanks Russell.

20.00 for a sensor? oh man, dont put a junky one in stick with quality AC delco!!! To answer your question, no you dont have to change both. The one before the cat converter is the only one that senses the air fuel ratio. The one behind the cat is only there to monitor cat efficiency. If the CEL isnt lit, just leave that one alone.

Hi- Thank you very much for your fast reply. And yes, you are right-it sounded like a scrappy one to me too-except for the fact that I live in Montreal Canada and a genuine one from GM is over $200.00. The one I bought on the internet with a 90 day guaranty,is coming from the U.S. and the seller assured me it was of excellent quality because it was Borg Warner, which I know sells quality products.Thanks again Russell.

Even the Cheapo heated o2's are $45 or so. I wouldn't trust a $20 heated o2.

i have the same car and wonder how you remove it. i am trying to replace mine but it is tight and hard to get a wrench in there. should i be trying when the manifold is hot?

On a different car I had to use an acetylene torch to get the one out to replace it.

you guys are trying way too hard....

Go to autozone or advance and rent (or buy) an o2 sensor socket for it. Make live WAY easier.

Plus O2 sensors are for the most part all the same size so one socket will probably work for most GM cars. Im gonna buy one here soon. They are cheap enough.

Actually I did have the socket and broke it. Bought another socket and then used the acetylene torch to heat up the o2 sensor. Got the sensor out very easy. Made sure to anti-seize compound on the sensor before putting the new sensor back in.

Well, i got mine out yesterday no problem. Removing it when the car was hot did the trick. I have the o2 socket also, but they are only good for installation. To remove it it is better to cut the wires and use a regular socket.

By the way, i used bosch sensors front and rear. Are they considered junk also as opposed to delco?

If it says Bosch on it,it is junk and my father does not trust anything made by Bosch.He has the worst luck anything made by Bosch.If you want to know,Bosch is a non profit company and this is what I heard.Most new O2 sensors have anti seize on the threads already with a plastic cap on the end.Snap On does have an O2 wrench out,I have seen one and it works.It has a breaker bar handle on with the oxygen sensor wrench on it and goes for about $85.00.

Hi-Ok, so I listened to you guys and I won't install a Bosch oxygen sensor in my Grand Prix. Up in Canada they are-Believe it or not-$175.00,but I found one on line, AC Delco # afs 109 for $40.00!!! Great Price. Russell.

Hi-Ok, so I listened to you guys and I won't install a Bosch oxygen sensor in my Grand Prix. Please post again if the new sensor improved your miledge. My 01 GT had been getting 26mpg before and dropped to 24.5mpg at about same time of having 10% ethanol in gas; this winter, I am down to 22mpg with same driving pattern/habit. I am contemplating new O2 sensor too.

Hi- If that 22 mpg is in the city, that's pretty good, but if it's highway - not so good - should be getting about 32-35 mpg highway. When I recieve my sensor, I am going to install it right away. I'll post later on if gas mileage improves and also if it was hard to install. Russell.

Hi- If that 22 mpg is in the city, that's pretty good, but if it's highway - not so good - should be getting about 32-35 mpg highway. When I recieve my sensor, I am going to install it right away. I'll post later on if gas mileage improves and also if it was hard to install. Russell.
I tried recently to have the oxygen sensor changed on my Grand Prix, but it wouldn't come out. GM tells me they can do the job, but most times, after heating with the torch, it will come out, but there is a very strong possibilty that some of the threads may stay stuck in the manifold therefore scrapping it and they are not responsible. They say not to change it anyway before the "check engine" lite comes on. So I guess I will just sell it.

[quote=russell350]Hi- If that 22 mpg is in the city, that's pretty good, but if it's highway - not so good - should be getting about 32-35 mpg highway. When I recieve my sensor, I am going to install it right away. I'll post later on if gas mileage improves and also if it was hard to install. Russell Hi-This is the last chapter in the saga of my oxygen sensor. I went to GM to ask about installation, and was told that, if the lite is not on,don't change it. I then asked ,if the lite was on, how much? They didn't seem to want to do the job for fear of screwing up the manifold.I couldn't believe that a GM dealer would act like this.I then went to a second dealer, and basicly got the same answer. WOW!!!! Unbelievable. I then took it to one of my friend's garage and he also couldn't believe what they had told me. He said he changes them all the time, and has never had a problem with the manifold or anything else. I brought my car in, and went to get 2 coffees at a nearby restaurent, and when I got back in less than 10 minutes, it was changed, without incident, and he chargerd me $15.00. I then checked out my gas mileage at the next fill up, and for sure,my mileage increased,maybe 2 0r 3 or maybe more miles per gallon. Thanks.