O2 sensors and gas mileage

[racorcey]

Now I know from experience on different cars that bad O2 sensors = reduced gas mileage, but.....

With respect to our cars, as many of our members have approached and passed the 100k mile mark, have you noticed any reduced gas mileage with the original O2 sensors still installed (front sensors, of course).

At one point in time, around the 50-75k miles point, I was able to achieve a best highway mileage of 27+ mpg, which was obtained, on average, at 65-70 mph, 50-60 deg F, flat road (NJ TP), and E10 fuel.

Currently, at 110k miles, the best I've been able to is about 24 mpg under the same conditions, except that fuel around here has been changed to E15 for the most part.

Now I know that the higher E rating of fuel will reduce gas mileage (thanks, EPA, for your idiocy), but I don't believe it would be about 10% less for the 5% difference between the two fuels.

I also understand that older, "lazy" O2 sensors can contribute to reduced MPG as well. I'm curious as to other list members here that have experience(s) in this area. In other words, after changing the sensors, did you see a reasonable change in gas mileage?

Thanks...

[ctrlraven]

I replaced my front O2 sensors after like 150-160k miles, didn't see too much difference on gas mileage though I went from having summer tires on to winter tires so hard to gauge mpg when I change the wheel/tire setup plus around here they have introduced winter blend gas so gas mileage is crap during November to March anyways.

[MOTOWN]

Im still on the original o2 sensors @102k but i havent seen any decrease in milage yet

[racorcey]

Well, I finally got around to changing the sensors on Sat, Apr. 21. The weather was just right. I did look up some past threads for help on changing the sensors, and did find some help, although it went from the sublime to the rediculous.

Took me about 4 hours, but that included:

- going out to buy a specialty tool in the middle of it all;
- having a floor jack quit on me (not while I was under the car!)...had to scrounge up another one;
- having to answer the phone several times;
- making the 200 ft round trip back and forth between my two garages for tools at least 10 times;

I found that the easiest way to replace the sensors was to remove the front wheels and the plastic inner fender wells. This gave maximal access without having to crawl either over or under the car.

The right side fender well was the easiest - two attaching screws and a four wire attachments - the well was out in about 5 minutes.

The left side (driver side) well was a bit more complicated, with all manner of flotsom screwed to it. It also required the removal of the air inlet hardware and the windshield washer container.

I started on the right side O2 sensor. Electical connector - no problem. Getting to the O2 sensor required that I go out an buy that specialty tool - the one that has a cutout for the wires, and is short enough to get into tight places. With some WD-40 soak, the sensor broke loose.

The left side sensor is obscured by the steering shaft, but I was still able to use the specialty tool to its advantage. The electrical connector was located behind the engine/transmission interface. I had to get a long screwdriver down to the release tab while simultaneously pulling on the wire to disengage it. Pretty bad location. Getting the new connector back on was about as bad.

I reset the PCM by pulling out relay 202. Now it will be interesting to see what happens on the next fillup.

Even more interesting was replacing the air filter several months ago - the original had about 110k miles on it. I picked up almost 2 mpg on that alone.

I broke the tabs on the electrical connector to the air bag pump, but it seemed to go together ok. If it have to, I guess I will tape it together. The metal tab that held the connector to the pump ass'y also broke off from rust. I have foam rubber surrounding that.

The other interesting item that broke off was the little white plastic box that has nothing more than a small rubber hose attached to it, and leads down to the air pump ass'y. I guess it comes from a relief valve. It's also embossed with "Marauder" on it. Interesting. Hopefully I can find another one.

And finally, when removing the window washer container, it literally fell off in my hands. It was missing one attachment bolt, and the only one holding it came off as I was starting to maneuver it for removal. I had to use a brass drift and hammer to re-seat the nearly stripped out screw holes in the fender that hold the container.

So - I did save some $$ doing it myself, considering the dealer wanted nearly $500 to do the job (with them supplying the sensors). Cost me about $100 for sensors and the tool - and my new found muscles that I didn't even know I had! :)

[RF Overlord]

Even more interesting was replacing the air filter several months ago - the original had about 110k miles on it. I picked up almost 2 mpg on that alone.Dude... :eek: :shake:
I broke the tabs on the electrical connector to the air bag pump, but it seemed to go together ok. Common...
The other interesting item that broke off was the little white plastic box that has nothing more than a small rubber hose attached to it, and leads down to the air pump ass'y. That's a "muffler" or "silencer" for the RAS vent. Just don't let the hose dangle down where it can get plugged with dirt.

Good on ya' for doing all this yourself...not only for the monetary saving but for the sense of satisfaction it brings. :up:

P.S. Change your air filter more often.............. :rolleyes:

[babbage]

No disrespect but I changed my o2 sensors in about 15 minutes, all you need is a 7/8" open end wrench. Unbolt o2 sensor, fish connector wire from above. Connect new o2 sensor, lower it down, then remove protective plastic cap. Twist connector wire backwards 15 times so after you open end wrench it back on the connector wire is normal (no twisties).

That's about it. Nothing else is necessary. Sorry you took the long way but at least it's done.

[ctrlraven]

One side took me about 15 mins and the other side took about an hour or so I believe.

[fastblackmerc]

+1 on changing the air filter..... cheap enough to change once a year....