It is on the rear exhaust manifold (near the firewall) where the 3 pipes join. It has a single wire coming out of the top. You probably won't be able to get a regular socket over it (especially not the new one) so try a wrench first. If you can't get the old one out, I usually just cut the old wire and use a deep socket with an extension. When you put the new one in you can just use a wrench then, it doesn't need to be that tight. That is pretty much it, plug the new one in and you are set to go.

I am one of many that has not had a good experience with Bosch, but if you go to your GM dealer AFTER checking the price at autozone (or autozone.com) they should price match with the delco from autozone (around $35), its a nice way to save about $20 on the GM list price.

Or if you are like me, and couldn't get the damn thing out to clear the firewall, to remove the header.. just break it. Take some pliers and snap the top off. Then you can use a regular wrench. Also, have some PB Blaster handy.. mine was on there real good.


-justin

Can also use a crowsfoot wrench. I have a deep socket with a slit up one side. AFS-20 (short) O2 sensor fits just fine, Bosch wire gets a bit cramped that the top.

With a 12" extension the O2 sensor is very easy to remove. I consider it a part of a tuneup.

BTW if you find a Delco jobber, the OTC price is about $24.

I've heard mixed stories about how hard it was to get it out, it all depends if the person who installed it last did it right. I just bought the O2 sensor socket with the slit up the side, but I could have probably just used a closed end wrench. Mine came right out with little force whatsoever. I've also heard of some people needing to replace thier entire exhaust manifold because the damn thing was fused on there. I bought the AC Delco AFS-20 off ebay for $19.99.

My 90 came right out but the 96 factory sensor was another story.
Had to soak it in penetrant for two days, start the car 5 min. to warm it, then install a cold socket on it to get it out (finally).
Used split socket with box wrench on it. The extension bar gave it too much torsional
twist.
I have a Bosch on there for 10k now with no problems. I would have gotten the Delco
though if I had known others had trouble.
If gas prices keep going up we may all be looking for Hybrids.

One thing I've found is going 65mph instead of 75 on the highway (if possible), it really makes a difference.

Agreed!!! I also agree with keeping the car in tune, tires inflated properly, et.al. But I can safely guarantee that if you try and drive in the "slow" right lane on the highway as much as possible you WILL increase your gas mileage by at least 3, 4, or more mpg. But chagning your driving habits can be as difficult as losing weight or quitting smoking. Some habits are tough to break.

On long trips with some hills, I find that driving at 75 is better than 65. That is when there is wide open road, no need to slow down and speed up again. I log every tank of gas, and this pattern has always been true. I always figured it was because at 75 I am doing about 2000 rpm, at 65 I am only doing 1750 rpm or so. So when the car hits a hill doing 65, it has to compensate more to maintain the speed since it does not have as much momentum. I am sure someone will disagree, just passing on what I have experienced over and over. This is a 350 mile trip, very little traffic, not using cruise, maintaining 75.

Keep in mind that cars of this era were designed for the National Speed Linit of 55 mph and will give the best gas milage between 50 and 60 mph (keep in mind that the EPA numbers were all calculated on a dyno and I seem to remember that highway was at 50 mph and why TCC lockup occurs just before that). From 60 to 80 the torque curve is pretty flat so most of the decrease is from drag but is very real. Above that it just goes downhil fast. Above 50 rolling resistance also becomes significant which is why proper inflation is important.

Today, all three of my 3800s- two "C"* and an "L" (Reatta, Bonneville, TranSport) get almost identical readings of 22-24 real mpg on the Interstate (70 mph limit) with the air on which makes no sense. I do think that with tinkering I could get a few more mpg out but just have not bothered since generally fill up once a month (home office).

At 12,000 miles per year and $3/gallon gas, the difference between 22 mpg and 30 mpg is $400. Significant but not worth the effort. Yet.

cars have not improved dramatically on MPG until recently.
I think you will see a lot of next generation cars in coming years with good MPG.
As far as our 3800'* I'm convinced the numbers are always lower than what they say you should get. Although highway numbers are usually right on.
Most of us get 25 - 28 highway but with them continually changing the gas formula'*
to cleaner burning who knows?