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New O2 sensors???
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spam Offline
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Post: #1
New O2 sensors???
I bought the dodge used, and it has been well maintained with around 140 K on it. Now it is at 155K and I am reading that O2 sensors get "tired" and should be replaced.

is there a way to test this?

highway voltages never exceeded 180 MV though I adjusted the efei to 220/250 range.

any thoughts on if and why they should be replaced?

I just bought an OBD2 scanner & software. Hopefully they will be in next week for analysis.

TIA
07-30-2009 03:05 PM
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colchiro Offline
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Post: #2
RE: New O2 sensors???
Depending on the sensor and who you talk to, we start thinking about replacing them by 50k miles or so and always by 100k. As they age, they start to slow down and lose the extreme voltage changes. I suspect the problem is heat and gasoline deposits. I know leaded gas shortens their life quickly too.

Mike can probably tell you what a marginal sensor "looks" like, probably easily visualized with an oscilloscope, which most of us don't own.

By any chance did you buy Mike's digital efie? That's more tolerant of a tired sensor.

Rick

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07-30-2009 03:28 PM
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RE: New O2 sensors???
Hey Rick

Thanks,

I do own a Tektronix 456! Dual trace - how cool is that?
07-30-2009 03:48 PM
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colchiro Offline
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RE: New O2 sensors???
Cool. I haven't owned one since I was a kid and that was army surplus.

I suspect if you know the min/max/freq measured from a warmed up vehicle, Mike can advise you.

Rick

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07-30-2009 04:39 PM
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spam Offline
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RE: New O2 sensors???
haven't a clue what to look for. and 456 is an IBM surplus ($50) i think it was around $650 new in 74

It's still a great scope. just current frequencies for computers are faster than the 456 can handle.

I have purchased some OBD2 computer software so I can plug a scanner into the USB port of my computer, and view on screendash board/stats. Got the OBD2 to USB of ebay for $30+/- 10%. Software was cheap if ---- you are willing to look around. Some was even free and other was cheap, some was expensive, and not being a pro shop I went for the best I could afford - trial and then purchase if happy.

would be great to have optimum and range readings to begin.

Mike - you there? any thoughts? recommendations?
07-30-2009 04:55 PM
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colchiro Offline
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RE: New O2 sensors???
(07-30-2009 04:55 PM)spam Wrote:  haven't a clue what to look for.

Sorry, I think you could connect the scope to the o2 output and to ground (the wire you need to cut, as documented in the installation docs).

So you'll have a rapidly changing voltage between 0 and 1 volt and if you note the height and frequency of that signal, I suspect Mike might be able to tell if it's good or tired.

Rick

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07-30-2009 05:57 PM
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mike Offline
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RE: New O2 sensors???
I'm sorry, I can't tell you whether its good or bad by what you see on the scope. I haven't viewed enough sensors on a scope to be able to do that. But you can hook up that scope and see clearly what the sensor is doing by tapping into the signal wire and ground.

If someone were to view sensors on a scope daily as part of their job, I believe they would be able to tell the difference. But I can't. I actually don't know of a good way to tell, other than to replace them as part of a proper maintenance schedule. As Rick said earlier in this thread, if they have over 100K on them, they must be replaced. You will get a mileage improvement just from that, so it's worth it.

He's also correct in that our Digital series EFIEs will work better with old sensors. All analog EFIEs (and also other manufacturer's digital EFIEs), don't work well with older sensors because they just add voltage to the sensor's voltage. To understand why our Digital EFIEs avoid this problem, you would need to read The New Digital EFIE: How It Works.

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07-31-2009 07:55 AM
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colchiro Offline
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Post: #8
RE: New O2 sensors???
Thanks Mike.

I thought you had advised someone that their o2's were "tired" based on the voltage range they report or something like that.

Although it's not recommended, it's probably cheaper to buy a digital efie than to replace just one o2 sensor. Blush

Rick

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07-31-2009 08:08 AM
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mike Offline
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Post: #9
RE: New O2 sensors???
Yes, well, it might be cheaper, but we still recommend changing them when they are due. I think there are enough variables when installing an HHO system, that we just don't want to have to worry about whether the sensors are working properly too.

Anyway, spam, if you don't change them out, just be ready if you have trouble getting your mileage gains. You may have to get them changed as part of the process to debug your system.

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(This post was last modified: 07-31-2009 08:51 AM by mike.)
07-31-2009 08:45 AM
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Post: #10
RE: New O2 sensors???
Hey Mike,

Glad I met you at St.pete show. Bought a dual efei from you I assume it was analog. I was the short fat ugly guy, so I assume you have no idea who I am. I'll make it easy - I was the one without the wifebeater t shirt.

Let me ask this... I just decided to change the O2 sensors as routine maintenance, BUT if it means anything I can do a before and after scope test. Though I don't have enough curiosity to do that unless there is some reason. Just curiosity , mine and yours is not enough to pull out the scope and do the stats, then return it and then report. I would imagine it would add an hour to the replacement, and to do that just to say "interesting" well I can say "interesting without an hours effort.

The MAP sensor is not yet installed but the efei and a rather robust HHO is, and with the old sensors it seems to be a bit more robust. No stats yet on the mileage. and the old sensors were returning 110 mv and I set the efei fore and aft to around 220~240. so I could be gaining power from just the efei.

anyway, new O2's next week, new OBD2 reader and software next week and I will be able to do statistical analysis on my laptop and compile logs. I suppose I can wait till the OBD2 software arrives before I do a O2 swap to get detail logs. That wouldn't be any extra effort and would satisfy my curiosity. I can report that? I suppose with HHO and without? and with and without new O2?

is there any value other than "that's interesting"?

what do you think?
07-31-2009 01:03 PM
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