I replaced the Oxygen sensor on my 93 Cadillac (230k mi) hoping to see some fuel economy improvement. The one in the car (presumabely original) was a Bosh, and worked fine. I replaced it with another Bosh unit identical in appearance anyway. I've been driving it around for several days and so far, there hasn't been any improvement in fuel economy. I am going by the average reading on the onboard fuel economy computer. Fortunately they are only $26. Just thought I'd share the results.

 

computer has to re-adjust to the new sensors....keep watching.

 

With that old engine, it will take more then an 02 sensor to bring it back up to it's old self. A serious tune up, rebuild the old carb, wire/plugs and a godd induction cleaning will bring her back.

 

With 230K you're probably looking at needing to free some rings, etc too. I'd do a compression test and see if any of them are well off where they should be. You may also have plugged cats, not sure the best way to test cat flow though. Both of those would affect mileage pretty badly. A proper injector cleaning or checking every injector for spray pattern and replace any showing issues will also likely help a lot. I'm not a fan of the blind induction cleaning in general though, running cleaner in fuel etc is fine but nothing beats pulling the injectors and looking.

 

I was expecting those same results when I changed the O2 sensors on my 2000 D2. Ended up having to go to the dealer to have them reset the 'adaptations' on the ECU. Otherwise I would have had to wait a couple of months ( for the miles that I drive)for the computer to relearn the new equipment

 

It takes months for the computer to react to new O2 sensors? Really? Do you know the cause for this seemingly long period of time? Please don't get me wrong - I am not doubting your word, it's just that my expectation is for a computer to react almost instantly to newly installed equipment.

 

It all depends on the mileage you drive, but the dealer said that even if I had erased the codes with my OBD2 reader, the ECU would have taken a while to go from the full rich O2 sensor fault mode, to the normal operating mode. Apparently, by reseting the adaptations in the ECU, the process is a lot shorter.

 

I'll keep watching the MPG, see if it shows any increase. Despite the high mileage, the car looks & runs great. Doesn't use any oil, I definitely keep up with maintenance. I probably could use some new wires though (thanks for the suggestion). I also replaced the CAT 2 yrs ago. These cars are built like tanks and not uncommon to run300k plus. Yeah, I could check compression and injector spray pattern, but all things being equal, if the O2 sensor had degraded (which I can't prove was the case) there should be some improvement in fuel economy, right? Well,I'll report back periodically as Iuncover more.

Has anybody use a generic Bosch O2 sensor on their L/R?

 

Just replaced all 4 O2 sensors in my Rodeo on Christmas Eve.Was down to 16 MPG avg from a high of 21 mpg avg when it was new...same kind of driving. Got back another 2-3 mpg in the first tank and am attributing the lack of a better improvement to the oxygenated fuels we're running in Denver in the winter.

Dave

 

Ok new to the forums here, great site BTW. I own a 98 disco I. My engine light came on and had it diagnosed at local shop (not LR but the guy who did it used to work there) and found out that I have 1 faulty O2 sensor... He was unable to tell me which one... ***4 mo. later*** had to replace the fan clutch this past weekend, got in the disco this AM and had a dead battery. Hmmm I jumped it and came to work. The whole way down the I-state I could feel it speeding up sporadically and I knew it wasn't me. I thought the CC might be acting up so I switched it off. Got of the I state and came to a light and I noticed my RPM's were high so I put it in neutral and they jumped to 3grand. revved it up thinking my throttle cable might be stuck... nope finally they settled on their own... Called LR and they said it was most likely the O2 sensor. I cant afford to take it to LR and pay $95 or replace all four. I know I know I shouldn't have bought a LR... Any suggestions... Can I unplug one at a time to see what happens??? Please help I cant afford burnt valves either...

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