When do you change O2 Sensors???

[Da Dark Jedi]

Three weeks ago I had to replace the wifes two rear O2 sensor in her Q45. The car had at that time 79500 miles, she mention to me that she notice an increase in gas mileage. So I did a little research in this matter and found out the lifespan of the sensors is about 80K.

So with the higher mileage Marauders out there, have anybody change their O2 sensors and when you did what results did you notice?

[fastblackmerc]

Almost 80k and still on the original O2 sensors.

[justbob]

Also depends a lot on your driving habits. Many cars go bad at around 60,000. if your car never see's a highway, then perhaps even earlier.

[MOTOWN]

95k and no problems yet

[Da Dark Jedi]

I hear people saying "No problems", does that mean your gas mileage has decrease or increase? Or do wait for the CEL to throw a code to inform you about it?

[MOTOWN]

no problems mean just that, no drop in mileage, no engine light a ok

[fastblackmerc]

no problems mean just that, no drop in mileage, no engine light a ok

Exactly!!!!!!!!

[ctrlraven]

158k miles on factory O2 sensors here. I've thought about replacing my front ones here soon and actually just went through emissions.

[Joe Walsh]

Most people think that their car's O2 sensors 'suddenly go bad' when they finally get a CEL.

The fact is that O2 sensor's performance slowly degrade over their service life. (service life is typically @ 75,000 -> 100,000 miles max.)

What happens is the sensors slowly lose sensitivity/have a broader dead span and don't 'toggle' back and forth as quickly as they do when they are new.

When they 'toggle' more slowly, the engine's computer is waiting for their signal and will default to the rich side as a safety measure.

(We all know what lean conditions do to engines, especially with today's high compression ratios and junk gasoline)

So you will get decreased performance and lower gas mileage as your O2 sensors slowly degrade.

I try to change mine between 50,000 and 75,000 miles.

I just did my Ranger's O2 sensors at 75,000 miles, even though I had no CEL/O2 code.

BTW: I've heard some automotive techs say that you shouldn't let O2 sensors go past 50,000 miles.

[ctrlraven]

Anyone have a part number for the front set of O2 sensors?

[Da Dark Jedi]

Most people think that their car's O2 sensors 'suddenly go bad' when they finally get a CEL.

The fact is that O2 sensor's performance slowly degrade over their service life. (service life is typically @ 75,000 -> 100,000 miles max.)

What happens is the sensors slowly lose sensitivity/have a broader dead span and don't 'toggle' back and forth as quickly as they do when they are new.

When they 'toggle' more slowly, the engine's computer is waiting for their signal and will default to the rich side as a safety measure.

(We all know what lean conditions do to engines, especially with today's high compression ratios and junk gasoline)

So you will get decreased performance and lower gas mileage as your O2 sensors slowly degrade.

I try to change mine between 50,000 and 75,000 miles.

I just did my Ranger's O2 sensors at 75,000 miles, even though I had no CEL/O2 code.

BTW: I've heard some automotive techs say that you shouldn't let O2 sensors go past 50,000 miles.



Thanks Joe & Justbob for eloquently stating a little known fact. There is a differance between a car that is performing "A OK" and one that is performing in OPTIMUM condition. So can you explain what these "Lean Conditions" will do to our engines over time? Anybody?

[Joe Walsh]

Lean conditions can lead to engine knock/pinging/pre-ignition.
Over time engine pinging will damage your rings and bearings from the constant pounding they are taking.
If you are running your car tuned to the ragged edge and you get significant knock, you can do some major damage....
Like broken pistons and rods through the block.
In our DOHCs, bad engine knock can cause the OEM oil pump gears to disintegrate....:eek:

[Da Dark Jedi]

Thanks again... In the Q45, the knock sensor on the same side went bad before the O2 sensor went totally out. The KS code was stored in memory and had no effect on emission or throw a CEL but the O sensor did throw the CEL. So I would think (correct me if I'm wrong) that people with over 100K or close to it, should consider this a maintenance item?

[ctrlraven]

Thanks again... In the Q45, the knock sensor on the same side went bad before the O2 sensor went totally out. The KS code was stored in memory and had no effect on emission or throw a CEL but the O sensor did throw the CEL. So I would think (correct me if I'm wrong) that people with over 100K or close to it, should consider this a maintenance item?
Yes, most O2 sensors run $40-50 a piece. There are part numbered ones for the Pre-Cat and Post-Cat. If you have a tune and the 2nd (Post-Cat) cats are most likely turned off so just worry about the fronts.

I found NGK O2 sensors from Advance AP for $44 each.
22060 is for the 1st set (Pre-Cats)
22500 is for the 2nd set (Post-Cats)

Advance AutoParts is running a special, order $100 more in parts and get $50 back to use between June 8th and July 9th

[Da Dark Jedi]

My Infiniti FSM states that the rears or post cats are the most important ones, it does give an explanation. Does the Marauder FSM state which set (more or less) has a determining effect?

[ctrlraven]

I would assume just the front ones are the most important since just about every Ford tuner turns the rears off on cars and trucks.

[Got_1]

Most people think that their car's O2 sensors 'suddenly go bad' when they finally get a CEL.

The fact is that O2 sensor's performance slowly degrade over their service life. (service life is typically @ 75,000 -> 100,000 miles max.)

What happens is the sensors slowly lose sensitivity/have a broader dead span and don't 'toggle' back and forth as quickly as they do when they are new.

When they 'toggle' more slowly, the engine's computer is waiting for their signal and will default to the rich side as a safety measure.

(We all know what lean conditions do to engines, especially with today's high compression ratios and junk gasoline)

So you will get decreased performance and lower gas mileage as your O2 sensors slowly degrade.

I try to change mine between 50,000 and 75,000 miles.

I just did my Ranger's O2 sensors at 75,000 miles, even though I had no CEL/O2 code.

BTW: I've heard some automotive techs say that you shouldn't let O2 sensors go past 50,000 miles.

Ditto! i was gonna post something similar until i read yours:beer:

[Joe Walsh]

This Popular Mechanics article does a pretty good job of explaining how O2 sensors 'toggle' back and forth around the perfect stoichiometric ratio.
As they get older they get less sensitive, or as they say in the article; "the O2 sensors get lazy" and their toggle rate slows down.

Link: http://www.popularmechanics.com/cars/how-to/maintenance/4219927

I understand that engine scanners and some tuners allow you to watch the O2 sensors toggle realtime.

.

[justbob]

Joe hit the nail on the head. These are in fact routine maintenance/tune up items. I swapped mine out two weeks ago at 80,000 because of slow cycling. Try to never buy anything but factory o2's, most usually they will not perform as well.

http://www.rockauto.com/catalog/raframecatalog.php

[stryker]

One of the first repairs done to BP74i was the replacement of the 4 Oxygen sensors followed by a change of almost all oils, only ones in schedule to replace are the differential and transmission.

[Joe Walsh]

Joe hit the nail on the head. These are in fact routine maintenance/tune up items. I swapped mine out two weeks ago at 80,000 because of slow cycling. Try to never buy anything but factory o2's, most usually they will not perform as well.

http://www.rockauto.com/catalog/raframecatalog.php

+ 1!

I was warned to only buy Ford Motorcraft 02 Sensors when buying replacements.

[ctrlraven]

+ 1!

I was warned to only buy Ford Motorcraft 02 Sensors when buying replacements.
I'll be picking up two Ford ones then.