Anyone ever replace O2 sensors that didn't code and get a gas mpg improvement?
- Thread starter Myco
- Start date
Icarus
Dedicated LVC Member
I'm susbscribing to see what everyone has to say. I'm debating doing this too 
rooster1969
Dedicated LVC Member
On my Mark, not yet, haven`t changed them. Different vehicle in the past, Yes.
Icarus
Dedicated LVC Member
I got a code 173 recently and am debating changing mine as the fuel pressure is good and trim values etc are too. I still need to double check the injectors but think that might be my next step...
I need to check my pump pressure myself.
Sapperfire
Dedicated LVC Member
O2 sensors, like shocks and struts, should be changed about every 50k. Fuel filter once a year, ect ect
MediumD
Dedicated LVC Member
Yes. The threshold for throwing a MIL is apparently very high, they've got to be pretty dead to throw a code. On an OBD1 anyway.
Lownslowlsc
Dedicated LVC Member
my buddy checked mine with his really expensive diagnostic tool and both were within limits, but 1 was "lazier" then the other by abit. There on my list along w/ new brakes as soon as i get a job. You can get a pair of o2's for around 50 bucks.
As far as i know there stock w/135k..
As far as i know there stock w/135k..
Lownslowlsc
Dedicated LVC Member
check max or rockauto..iirc oem are around 50 each at ra.
2002WRXSTi
Dedicated LVC Member
I just turned 110k and along with plugs I should do them to and see if it makes the car better or not 
chris2523
93 Mark VIII
depends. obd1 has 2 fronts. obd2 has 2 fronts and 2 rears. 4 total.
i think.. pretty sure.
Sapperfire
Dedicated LVC Member
The front 2 are needed on the obd2, the rears can be tuned out
Rich88LSC
Dedicated LVC Member
They al;l need two fronts. The rears are for OBDII cars and do nothing except monitor cat efficiency.
2002WRXSTi
Dedicated LVC Member
My 96' was like that, the colder it was the worse it seemed to run? Sometimes it didn't even seem to want to start?!
I did plugs, wires and filters when I first picked it up at 133k and it would fall on it's face when it was cold. At 209k when the trans finally wet the bed it was running somewhat OK in the cold? It never threw any cells when it was cold, just ran like crap
At least my 98' seems to be good so far in the cold. My biggest gripe is that my drivers side heated seat ain't working
96_Lincoln_LSC
Dedicated LVC Member
I had the same problem and it wasnt throwing a code.. if your GEN 1, you may want to look at getting yourself a new IAC.. let me just tell you PITA.....
No fun and no room. the two bolts are 8MM and if you remove everything on the top like wiper motor assembly, covers and then remove the TB, it will make life easier. and Oh BTW, Dont cross thread the bolts putting it back on.. you'll never get this to seal correctly.
just my 2 Cents.
Bill
Moes8
Dedicated LVC Member
yes, i changed mine without a code and the car went from 18 mpg highway to 26-27 instantly,i had a rough idle and miss at 2000 rpms but no code, i checked/changed everything,then i did the o2's and bam,it was all good
thaywood
Dedicated LVC Member
That's what I need to do to my '96. It's down to 20.2mpg now and it has a rough idle and miss between 2000 and 2500 RPM. Did you replace all four O2's or just the two upstream of the cats?
Roadboss
Dedicated LVC Member
The fuel pump and filter are maintenance items, so you should prepare for it, and get it taken care of if you are starting to have real problems with them. I ditched the ones on my DD at the same time I got the O2's replaced as the car had 125M on it.
Green Machine
Dedicated LVC Member
Myco,
Im curious what Brand and Octane Gas you are using.
I switched brands of gas in early December, and my gas mileage dropped approx 5 mpg. Now, i do not know if thats from the companies switching over to their winter blend, or if its a Brand thing. i always use the highest octane i can find, ie: 91-93.
Im curious what Brand and Octane Gas you are using.
I switched brands of gas in early December, and my gas mileage dropped approx 5 mpg. Now, i do not know if thats from the companies switching over to their winter blend, or if its a Brand thing. i always use the highest octane i can find, ie: 91-93.
Moes8
Dedicated LVC Member
i have a 95, i only did 2 sensors
I run 93 octane. I chased down stumbling problems starting 5 months ago. Turned out to be a bad COP. Then 2 months later another COP went bad. I've since replaced 5 ( any that didn't ohm out correctly I replaced.) The problem is that 2 of them are different brands from the other 3 new ones. I had the car apart and got a ride to the store and they were out of what I was using so I had no choice but to do with another brand.
Before the COP change I had replaced the plugs, boots, fuel filter. Done the Seafoam and MAF. I replaced the AIC 2 yrs ago.
This problem has actually started very recently. 2 weeks ago I had the injectors cleaned by my mechanic and 2 days after that I had a header gasket replaced sealing up the exhaust for the first time since I got the car.