Wideband O2 sensor lifespan?
 

I've searched/looked but not finding much on this related to CIS cars.

I have an AFR gauge installed with a Bosch LSU 4.9 (I originally posted this as LSU 4.2 - wrong...) wideband sensor on my 75 911 with a 2.7 and mostly-stock CIS. I'm only getting ~ 3 years (and ~8k miles) out of a sensor before it dies. I've tried cleaning these but no luck there. I have this solely to monitor the CIS and try to catch issues before they get too big.

The exhaust is SSI's and factory muffler. I'm running unleaded fuel.

What are the rest of you seeing for O2 sensor lifespan?

There are as many fake BOSCH 4.9 LSU sensors available out there as there are Gucci bags. They are often recognized by cheap offers below the usual BOSCH prices, so make sure you have an original installed. The sensors don’t need cleaning, in fact, that can break them. Just screw them in and you’re done. My LSU 4.9 has been installed for 8 years now and... no problems.

I have had the same Bosch sensor for the last 15+ yrs. I don't know what version it is, but could check - I have a spare. It is subject to the most extreme conditions any sensor would experience. Turbo mostly at WOT.
I don't run leaded fuel, but have been told by some it is not the issue people expect. But all the same, I have avoided it. I know others who run avgas and still get a useful life.
One thing that does damage them I think is moisture/condensation on warm up. Not sure how you control that but I believe they have a heating element to keep moisture off the surface of the sensor in warm up. Maybe where it is the exhaust and how much moisture it experiences is an issue? Apart from possibly not being the genuine article.
Alan

If your car runs with a way too rich mixture the O2 sensor gets poisoned quickly and is crap afterwards. You cannot clean them! Any cleaning attempt will break them too. Bosch delivers them with just a tiny kiss of grease on the thread and a plastic protection cap for the tip. If this grease gets to the tip of the sensor due to improper handling, that grease will melt on the first engine start and destroy the sensor undoubtly. These sensors are very sensitive for mechanical shocks and ungentle handling. Once mounted do not dismount it again unless it's bad.

Condensed water also may damage them. Again a vote for proper mixture, even on cold start. They got mounted overhead/upside down to prevent watering them too. The heater of an O2 sensor is not intended to keep them dry, it's only to get them quicker to work after engine start as their operating temperature is about 300°C and more...also the heater keeps the sensor hot when engine idles on traffic lights etc. The heater runs all the time.

https://www.hella.com/hella-za/assets/media_global/HASA_Lambda_Brochure_LRes.pdf

https://www.hella.com/techworld/us/technical/sensors-and-actuators/test-lambda-sensor/

https://www.bosch-motorsport.com/content/downloads/Raceparts/Resources/pdf/Data%20Sheet_69034379_Lambda_Sensor_LSU_4.9.pdf

A proper operating O2 sensor must last in modern cars up to 50.000mls and more. Porsche recommended on the lambda SCs like mine, a checking interval of every 30.000 mls iirc...
It may depends on how close to the exhausts of the cylinder heads the sensor is mounted. Propably when it gets too hot this is also not wanted. Also banging into the exhaust by releasing throttle will damage them too...again a thing of mixture...

Many sources for faults...

Thomas

Thank you all for your input..

Info regarding sensor lifespan...and other info

https://wbo2.com/lsu/Y258K01005e03mar21eng.pdf

https://wbo2.com/lsu/lsu4.htm

Really nice website!
+1

I just replaced original on mine. It lasted 10-15K miles. Its in a bung in the SSI headers fairly close to muffler attachment. On the off hand you could check the wiring and see if that is your common failure point, but most likely not.

the culprits
Fuel additives? something you add or something in your local/regular fill up
Cheap O2 sensor, I just bought a cheap one off amazon, if it makes 5-10k id call that good value
Your mix ratio? my best bet is ethylene glycol poisoning
http://forums.pelicanparts.com/uploa...1741799499.jpg

Switch to a Denso, NGK or NTK.. The Japanese ones are faster and last longer.
"03-"09 Cadillac STS, SRX 12575657
2000-"02 Subi Forester, Upstream:
Denso 234-5003
NGK 243-20
NTK 243-21
AutoMeter 0 258 007 366 is Bosch

Great info - thanks, everybody.

TimT - That PDF link is terrific! Thanks for that!

After reading all this stuff, I think I have a combination of issues:

#1 - Sensor placement - I'll admit that I was hesitant to carve up my SSI's so the O2 sensor is currently installed in the inlet pipe of my stock muffler. It may be just too cold. I'll have to get a thermocouple in there and see what the exhaust gas temp is. I probably need to move the sensor bung closer to the collector junction.

#2 - I have old, open-loop CIS so it's running relatively rich (~12.2 AFR) at cold idle. I'm at 13.8 AFR warm idle (which correlates to the CO mix it's supposed to have). I do get a lot of water vapor condensation when cold.

#3 - Deposits. I don't really burn engine oil (1/2 quart in ~5000 miles - probably dripping out somewhere) but I do add ~4 oz of Mystery Marvel Oil per 10 gallons of fuel to keep the CIS lubed. I know - snake oil - but it runs wells and it gets angry when it's not there.

Couple of questions:

Mtsurfposse - I'm not understanding your comment about ethylene glycol poisoning. Where would that come from? No antifreeze...

Old H2S - Do you know if the NGK or NTK items are drop-in replacements for the Bosch LSU 4.2?

That’s my version of humor

Ha! Got it.

Interesting.

Temporary richer mixtures are no problem for OX sensors, especially known from cold runnings. All Lambda based engines are running open loop during cold running.

Especially for Wideband sensors, richer mixtures even driven permanently are no big problem, as such sensors are also used without problems on race engines where such wideband sensors are used to keep mixtures on the wanted target rich side, for max performance. Maybe the lifespan here actually is reduced, but not in a way the TO reports.

As mentioned previously, watch out for counterfeits.

These issues go back a decade or more:

https://news.bmotorsports.com/beware-fake-ntk-sensors-are-flooding-the-market/

I have used the Ballenger AFR 500, and only bought sensors from them. They have been paying a lot of attention to their supply chain for a long time.

I have also used AEM. If I were to try them again, I would only buy replacement sensors from them.

My application exposes sensors to leaded fuel. Some sensors hold up better with leaded fuel than others.

Companies like Denso and Niterra are getting ready for a different future! Both have had silly con valley outfits for quite a while.

Niterra have beautiful offices!

Bosch 4.2 is the architecture type.. Any 4.2 uses the same plug connector. The numbers listed are all 4.2"s. the only difference is the length of the cables.
And look out for counterfeits, really, trust no one. How I found all the numbers is calling Denso, NGK and NTK and asking if I can buy direct because I keep getting sold junk and they will if you ask please. I have taken a lot of heat here for going direct and paying full nose bleed prices from the manufacturer. I lost one of my Mustang race motors in 30 minutes from junk parts, the MFG was surprised by someone using original boxes and had to step up their controls.

All of this is true. You can poison a sensor quite quickly. Leaded gas will do it real fast - so will a lot of unburnt (even unleaded) gas in the exhaust - like from a plug not firing.

The Bosche LSU 4.9 tech note that MoTeC provides states that sensor lifetimes are highly dependent of application, and that typical lifetime in a high performance engine is 500 hours for unleaded fuel and 50 hours in leaded.

It also says: Most of the installation information seems to be paraphrased or condensed versions of the information Bosche provide in "Technical Product Information" document Y 258 E00 015e, dated 2005. No idea where you might find this now (I downloaded it from the Bosch Motorsport site in Oz before they removed a whole bunch of stuff). But it's very specific about placement, angles, treatment, storage, vibration etc.

Although LSU 4.0, 4.2 and 4.9 sensors are all different families, I'd expect most of the information for their care and feeding to be similar.

The symptoms of an old or poisoned sensor is that it becomes slow to react, or has drifted significantly from the original calibration number. They don't get better....

If you happen to know what the calibration number originally was (MoTeC-supplied Bosche sensor will comes with this number scribed on the sensor body), you can compare to the number you get from a free-air calibration now - which will give you an idea of the drift.

(The calibration number is directly related to the laser-trimmed resistor packaged in the sensor at the factory. And the free air calibration is used to correct for drift. At one time, a long time ago, Innovate were getting lots of internet heat from owners wjho said theuy had to free air calibration way too often and throw away many sensors. I thought the AEM UEGO had a better rep, but never used either myself<shrug>)

A MoTeC "gold box" ECU will show you this calibration number; no idea how you display it if you don't have one.

However, from the MoTeC forum:

It is possible to buy genuine Bosche LSU 4.9s on (for example) Amazon. For a pretty reasonable price. I did.

I tested the resistance between on my 4.9 pins 1 & 6 as described above, and, after the free air calibration procedure, the calibration number reported by the M800 matched very closely (a variation of 2 or 3 on a value over 5-600, IIRC). YMMV.

Hint

https://wbo2.com/lsu/Y258K01005e03mar21eng.pdf

Two reasons they can fail quick
1 - Leaving them in exhaust stream disconnected or not powered up. If they are not heater controlled by the controller they will fail fast.
2 - Some aftermarket wideband controllers have very poor heater control. LM-1 controllers are notorious for burning up sensors.

Thanks for the additional info. I'm pretty sure that I've received legit sensors; I will be careful about purchasing the replacement. I may try NGK or NTK.

I've got the Innovate MTX-L gauge; not sure how good that controller is.