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O2 sensors change intervals


Canuck2

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Wondering if the sensors should be changed at a specific millage interval or wait for a change in fuel millage (before and after the cat). Have been told every 60 thousand miles, don't mind changing things for maintenance but not just to change things, don't have a ob2 reader but truck runs fine so just wondering. Truck is 2009 fx4 at about 55000 miles.
 


adsm08

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I usually say 100K is a good maintenance interval for oxygen sensors. They aren't really a wear item, but do live in a very harsh environment and so they loose efficiency over time.
 

Canuck2

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Thank you for the reply sir, guess I'll leave them for awhile then, can you suggest a reasonably decent scanner (ob2) that would work well with my 2009 4ltr ranger.
 

RonD

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O2 sensors use a chemical reaction to detect oxygen levels in the exhaust
Much like car batteries use a chemical reaction to store and release voltage

So they do wear out, chemicals get depleted, just like car batteries
O2 sensor part generates its own voltage
.1 volt is Lean
.9 volt is Rich
As the chemicals deplete, voltage goes down(like a battery), so False Lean condition occurs and computer adds more fuel than needed, it ain't much, but ain't 0 either, lol.

If you have engine air/fuel mix problems or oil is leaking into intake then that can shorten the life of O2s, and Cat converters, lol.

But I agree with adsm08, 100k is a reasonable life span for Upstream O2s, replacing them every 100k would probably be free in fuel savings over that 100k
Downstream O2s tend to last much longer
 

adsm08

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O2 sensors use a chemical reaction to detect oxygen levels in the exhaust
Much like car batteries use a chemical reaction to store and release voltage

So they do wear out, chemicals get depleted, just like car batteries
O2 sensor part generates its own voltage
.1 volt is Lean
.9 volt is Rich
As the chemicals deplete, voltage goes down(like a battery), so False Lean condition occurs and computer adds more fuel than needed, it ain't much, but ain't 0 either, lol.
Right. What I meant by "not a wear item" is that an oxygen sensor is a wear item like an ignition coil is a wear item, not like a break pad is a wear item.

The average person who only owns a vehicle for five or six years usually will never need to replace one unless it failed prematurely, and you will almost never have your service adviser call you and say "Your oxygen sensor is near the end of it's life and should be replaced".
 

pjtoledo

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Thank you for the reply sir, guess I'll leave them for awhile then, can you suggest a reasonably decent scanner (ob2) that would work well with my 2009 4ltr ranger.
apps for a smart phone are cheap, Forscan for a PC has a free version. you need to buy an ELM327 adapter ($25-50) that plugs into the OBDII port and sends either Wi-Fi or Bluetooth to your device of choice.
another app is Torque. I picked up a Forscan, still stumbling around with it. proficient users can do a lot with it. there is some good info on it at ford-trucks.com
 

Canuck2

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Thank you sirs for the info.
 

RonD

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And just a "heads up" I had a mechanic reverse my two upstream O2 sensor wires, they have universal plugs so no left or right difference.

Picked up the truck, ran fine then after about 4 minutes it started running poorly, and Check engine light came on, this truck had never had CEL come on before, 1994 4.0l

There was a longer uphill section on the drive home and I noticed when I went to WOT(wide open throttle) the engine smoothed out and ran fine, if I let off the gas a bit it started to run poorly.

Anyway read the codes, codes were bank1 lean, bank 2 rich ??
Cleaned MAF
Checked spark plugs
Engine ran better then after a couple of minutes started running like crap and CEL came back on

Started thinking, yes it hurt, lol.
O2 sensors are not used on Cold Start, they need to be warmed up to 600+degF to start working so computer ignores them until coolant temp gets above 140degF or so.

Computer also ignores O2 sensors at WOT, it runs a Rich mix for best power, assuming driver doesn't care about MPG just Power with foot to the floor :)

Only 1 wire color difference between left and right O2s, and that was it, swapped them back and all was well.

Mechanic wanted me to bring it back so he could fix it...............wonder what that would have cost me, lol.

So do O2s one at a time, or make sure you know which connector is for which side


Or if you want to sabotage someones car ....................
 
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craveman85

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Mine have 230k and they're still working good.
 

RonD

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Mine have 230k and they're still working good.
That would be unique for upstream O2 sensors

O2 sensors start to read Lean as they get older and chemical gets used up, so computer will run the engine Richer than it needs to so MPG goes down a bit, O2 is still "working" just not as efficient as when new.
The $80(for 2) cost to replace them more than pays for itself in fuel savings over the next 100k

Downstream O2s can last the vehicles life, so 230k wouldn't be unique
 
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Denisefwd93

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Let me restart this discussion about O2 sensors, there are so many and the prices vary wildly! I'm seeing prices from $25 to $80 each!
 

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