Guys, last week, my check engine light came on after a y-pipe gasket fix. Got home and put the code reader on and had codes for the 2 front O2 sensors. Took them off, shop vac'ed them and sprayed them with brake cleaner, re-installed them and erased the codes. The light never came back on.

But since I had changed my 2 rear O2 sensors last winter, I decided that it might be a good thing to change the front ones also, since I have 58000 miles on the counter, and the previous owner had used no so clean gas when he was in europe. It was also my understanding that with time, the O2 sensor diminish in performance and can cause our already hard on gas vehicles to be even harder.

Wellllllll........After1/2 a gas tank with new O2 sensors, my truck seems to be even harder on gasthan before. I was expecting to see a remarquable difference right away, well, I do see a difference, but on the wrong side of the spectrum[:@]

Please tell me that it takes a few weeks before the truck relearns the new readings or whatever...........


Wassup with that????

 

So, first of all it is pretty early to replace the 02's unless one failed.
Why did you replace the rear 02's?
If you replace all four 02's, and the ones coming out were shot, then you should notice a change as soon as you start up and go.
I would never suggest cleaning your 02's with any cleaner, it usually kills them.
The 02's that you put in the rear, were they plug and play or universal?
Change out the fronts.

 

The back O2 were killed last winter by me trying to use a mix of Acetone in my gas to clean things up. I had been using it in my Jeep with no problems, and since I had just acquired the truck, I thought that a good clean up was in order. Let's just say that after about 10-15 miles with that stuff in the tank, It smelled really bad from the goo being burned by the cats, and the check engine light came on and the rear O2s were shot.

Now after the y-pipe exhaust leak fix last week, the check engine light came on again and this time, I had codes for both front O2 sensors. As said earlier, I took them off ,cleaned them, reinstalled them and erased the codes. But although the check engine light did not come on after 3 days, I decided to go ahead and change both front O2s, instead of ending up with that light coming on in a few days, weeks, months or whatever, I just wanted to change them and get it over with, thinking that they had probably lost some performance and that I would regain a bit of loss fuel economy. And by the way, all 4 O2s are Land Rover O.E.M.

 

So, you have replaced all 4 of the 02's and you believe you are lacking in power?
How much acetone did you use, ounces per gallon?

 

Not power, the power is there and everything. My surprise is that expected to get better m.p.g after the replacement, but not only are there no gains, it seems worst on gas than it was.

Thing is that I justified to myself replacing those O2 sensors would maybe get me 1 -2 m.p.g better than it was. That way, sooner or later, I would get the expense of the sensors($200.00) back in fuel economy. Talk about pissing against the wind.

I have a D2 with a 2 inch O.M.E lift and run 265/70r16 tires with stock gears. I know that this is not a receipe for fuel economy, but I run full synthetics everywhere and havereplaced the spark plug wires with magnacores last summer. I run only premium fuel, and get 12-13 m.p.g with a mix of 80% city and 20% highway driving. Personnaly, I think that this sucks.

Now don't get me the Honda Civic line, cause up here, premium fuel is the equivalent of $4.90 a U.S gallon !!! Just thought that new O2s would have helped. Cause I've heard numerous times about people with 9-10 m.p.g getting 15-16 after changing sensors.

 

If you had waited until the 100,000 mark, your 02's would have lost enough punch that upon replacement, you would have noticed an increase in MPG. In town mileage is always bad, I get about 12MPG yet on the road, here in Colorado at 7000 foot elevation I can pull around 18.5 at 65 MPH.

 

All right, another gas tank later, I'm down to 9 m.p.g. In trying to find the possible reasons that would explainthe previous drop, I re-installed the K&N air filter and started using 3rd gear on the tranny around town, and this combination got me 9 m.p.g[]

So, since it didn't help and actually almost hurt my mileage, I took out the K&N again and I'll wait till later to do the 3rd gear thing.

One thing that I did find, was that the freezing cold weather has caused my tire inflation to go down to 30 psi rear, and some 20 psi front. So I put it back to 38 rear and 30 front. I know that this alone cannot be responsible for a 4 m.p.g drop, well, this and winter gas, but it can't hurt right ???

So I'm now pretty puzzled by all this. The truck idles, runs and actually sounds super smooth now that I finally got the y-pipe exhaust leak that I've been chasing since last spring, and I have no lights on the dash that are on, and for some reason I seem to be running rich. it's been almost a month since I replaced the front O2 sensors, and I'm now wondering if it takes a while for the ECU to recognise the new sensors and their reading, or if I need to bring it down to the dealer for a reset of some kind after replacing the said O2s. I used my OBD2 reader and reseted the computer after installing the new sensors and if I re-read it it shows O no codes, but maybe it is required to go deeper in the programming or something.

Any thoughts ???

 

Go to 35 and 40 for air pressure, get rid of that K&N if you don't want t o replace your MAF. Has your gas been changed to the wnter mix, that will cause a drop in mileage.

 

Yep, nothing but winter gas around here. I'll up the psi tonight. The K&N was only kept cause I couldn't bring myself to throw it away. It was out and it's out again after deeing that it didn't improve my mileage. So Mike, do I need to go to the dealer to reprogram the ECU, or does it take a while to relearn the new readings, or what ???

 

Not sure how the O2 readings are, but if your truck is used to newer sensors in the rear, you could swap the fronts out with the rear. I know that is a lot of work, but it should but you back in the same situation you started with.

Also, the air pressure will mess with your mileage. Especially on those big meats.